Projection device, image correction method, and computer-readable recording medium

ABSTRACT

A projection device includes a projection unit including a display element in which pixel lines each formed by pixels arranged in a first direction are arranged in a second direction and an optical system that projects light emitted from the display element and projecting an image based on input image data, a first correction unit for correcting a scale of each line data of the image data that corresponds to each of the pixel lines, a second correction unit for correcting a second-direction scale of each pixel data of the image data after the correction performed by the first correction unit, and an image cutting-out unit for cutting out image data of an area, which is projected from the projection unit, of the image data after the correction performed by the second correction unit and input the image data of the area to the projection unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of PCT International Application No.PCT/JP2014/051726 filed on Jan. 27, 2014 which claims the benefit ofpriority from Japanese Patent Application No. 2013-013552 filed on Jan.28, 2013, Japanese Patent Application No. 2013-017507 filed on Jan. 31,2013, Japanese Patent Application No. 2013-026529 filed on Feb. 14,2013, and Japanese Patent Application No. 2013-076025 filed on Apr. 1,2013, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a projection device, an imagecorrection method, and a computer-readable recording medium.

2. Description of the Related Art

A projection device such as a projector device is known which drivesdisplay elements based on an input image signal and projects an imagerelating to the image signal on a projection face of a projection mediumsuch as a screen or a wall face. In such a projection device, in a casewhere a projection image is projected not in a state in which an opticalaxis of a projection lens is perpendicular to the projection face but ina state in which the optical axis of the projection lens is inclinedwith respect to the projection face, a problem of a so-calledtrapezoidal distortion in which a projection image originally projectedin an originally approximate rectangular shape is displayed to bedistorted in a trapezoidal shape on the projection face occurs.

Accordingly, conventionally, by performing a trapezoidal distortioncorrection (keystone correction) for converting an image that is aprojection target into a trapezoidal shape formed in a directionopposite to that of the trapezoidal shape formed in the projection imagedisplayed on the projection face, a projection image having anapproximately rectangular shape without any distortion is displayed onthe projection face.

For example, in Japanese Patent Application Laid-open No. 2004-77545, atechnology for projecting excellent video for which a trapezoidaldistortion correction has been appropriately performed onto a projectionface in a projector also in a case where the projection face is either awall face or a ceiling is disclosed.

In such a conventional technology, when a trapezoidal distortioncorrection (keystone correction) is performed, an image is convertedinto a trapezoidal shape formed in a direction opposite to a trapezoidalshape generated in a projection image according to a projectiondirection, and the converted image is input to a display device, wherebythe keystone correction is performed. Accordingly, on the displaydevice, an image having the number of pixels that is smaller than thenumber of pixels that can be originally displayed by the display deviceis input in the trapezoidal shape formed in the opposite direction, anda projection image is displayed in an approximately rectangular shape onthe projection face onto which the projection image is projected.

In the conventional technology as described above, in order not todisplay an area of the periphery of the projection image onto which theapproximately rectangular-shaped original projection image is projected,in other words, a differential area between the area of the projectionimage of a case where no correction is made and the area of theprojection image after the correction on the projection face, image datacorresponding to black is input to the display device, or the displaydevice is controlled not to be driven. Accordingly, there is a problemin that the pixel area of the display device is not effectively used. Inaddition, there are cases where the brightness of the actual projectionarea decreases.

Meanwhile, recently, in accordance with wide use of high-resolutiondigital cameras, the resolution of video content is improved, and thus,there are cases where the resolution of the video content is higher thanthe resolution of a display device. For example, in a projection devicesuch as a projector that supports up to full HD of 1920 pixels×1080pixels as an input image for a display device having resolution of 1280pixels×720 pixels, the input image is scaled in a prior stage of thedisplay device so as to match the resolution such that the whole inputimage can be displayed on the display device, or a partial area of theinput image that corresponds to the resolution of the display device iscut out and is displayed on the display device without performing suchscaling.

Even in such a case, in a case where projection is performed in a statein which the optical axis of the projection lens is inclined withrespect to the projection face, a trapezoidal distortion occurs, andaccordingly, it is necessary to perform the trapezoidal distortioncorrection, and similar problems occur at that time.

The present invention is devised in consideration of the descriptionpresented above, and an object thereof is to provide a projectiondevice, an image correction method, and a computer-readable recordingmedium capable of easily acquiring an appropriate projection image.

SUMMARY OF THE INVENTION

It is an object of the present invention to at least partially solve theproblems in the conventional technology.

There is provided a projection device that includes a projection unitincluding a display element in which a plurality of pixel lines eachformed by a plurality of pixels arranged in a first direction arearranged in a second direction perpendicular to the first direction andan optical system that projects light emitted from the display elementand projecting an image based on input image data; a first correctionunit configured to correct a scale of each line data of the image datathat corresponds to each of the pixel lines based on a position of theeach of the pixel lines in the second direction in the display elementand a second-direction component of inclination of a projectiondirection of the projection unit with respect to a normal line of aprojection face onto which the image is projected; a second correctionunit configured to correct a second-direction scale of each pixel dataof the image data after the correction performed by the first correctionunit based on a position of each pixel in the second direction in thedisplay element and the second-direction component of the inclination ofthe projection direction of the projection unit with respect to thenormal line of the projection face onto which the image is projected;and an image cutting-out unit configured to cut-out image data of anarea, which is projected from the projection unit, of the image dataafter the correction performed by the second correction unit and inputthe image data of the area to the projection unit.

The above and other objects, features, advantages and technical andindustrial significance of this invention will be better understood byreading the following detailed description of presently preferredembodiments of the invention, when considered in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram that illustrates an example of theexternal appearance of a projector device that can be applied to becommon to each embodiment;

FIG. 1B is a schematic diagram that illustrates an example of theexternal appearance of the projector device that can be applied to becommon to each embodiment;

FIG. 2A is a schematic diagram that illustrates an example of theconfiguration for performing rotary drive of a drum unit that can beapplied to be common to each embodiment;

FIG. 2B is a schematic diagram that illustrates an example of theconfiguration for performing rotary drive of the drum unit that can beapplied to be common to each embodiment;

FIG. 3 is a schematic diagram that illustrates each posture of the drumunit that can be applied to be common to each embodiment;

FIG. 4 is a block diagram that illustrates the functional configurationof the projector device that can be applied to be common to eachembodiment;

FIG. 5 is a conceptual diagram that illustrates a cutting out process ofimage data stored in an image memory that can be applied to be common toeach embodiment;

FIG. 6 is a schematic diagram that illustrates an example of designationof a cut-out area of a case where the drum unit that can be applied tobe common to each embodiment is located at an initial position;

FIG. 7 is a schematic diagram that illustrates setting of a cut-out areafor a projection angle θ that can be applied to be common to eachembodiment;

FIG. 8 is a schematic diagram that illustrates designation of a cut-outarea of a case where optical zooming is performed that can be applied tobe common to each embodiment;

FIG. 9 is a schematic diagram that illustrates a case where an offset isgiven for a projection position of an image that can be applied to becommon to each embodiment;

FIG. 10 is a schematic diagram that illustrates access control of amemory that can be applied to be common to each embodiment;

FIG. 11 is a schematic diagram that illustrates the access control ofthe memory that can be applied to be common to each embodiment;

FIG. 12A is a schematic diagram that illustrates the access control ofthe memory that can be applied to be common to each embodiment;

FIG. 12B is a schematic diagram that illustrates the access control ofthe memory that can be applied to be common to each embodiment;

FIG. 12C is a schematic diagram that illustrates the access control ofthe memory that can be applied to be common to each embodiment;

FIG. 13A is a schematic diagram that illustrates the access control ofthe memory that can be applied to be common to each embodiment;

FIG. 13B is a schematic diagram that illustrates the access control ofthe memory that can be applied to be common to each embodiment;

FIG. 14 is a diagram that illustrates the relation between a projectiondirection and a projection image projected onto a screen that can beapplied to be common to each embodiment;

FIG. 15 is a diagram that illustrates the relation between theprojection direction and the projection image projected onto the screenthat can be applied to be common to each embodiment;

FIG. 16A is a diagram that illustrates a conventional trapezoidaldistortion correction;

FIG. 16B is a diagram that illustrates the conventional trapezoidaldistortion correction;

FIG. 17 is a diagram that illustrates an image projected onto aperpendicular face that can be applied to be common to each embodiment;

FIG. 18 is a diagram that illustrates the image projected onto theperpendicular face that can be applied to be common to each embodiment;

FIG. 19 is a block diagram that illustrates the functional configurationof a projector device according to a first embodiment;

FIG. 20A is a diagram that illustrates cutting out an image of a partialarea of input image data;

FIG. 20B is a diagram that illustrates the cutting out the image of thepartial area of the input image data;

FIG. 21A is a diagram that illustrates the cutting out the image of thepartial area of the input image data;

FIG. 21B is a diagram that illustrates the cutting out the image of thepartial area of the input image data;

FIG. 22 is a diagram that illustrates an image of an unused arearemaining after the cutting from the input image data according to thefirst embodiment;

FIG. 23 is a diagram that illustrates a projection image of a case wherea geometric distortion correction according to the first embodiment isperformed;

FIG. 24 is a diagram that illustrates major projection directions andprojection angles of the projection face according to the firstembodiment;

FIG. 25 is a graph that illustrates relation between a projection angleand a correction coefficient according to the first embodiment;

FIG. 26 is a diagram that illustrates the calculation of the correctioncoefficient according to the first embodiment;

FIG. 27 is a diagram that illustrates the calculation of lengths oflines from the upper side to the lower side according to the firstembodiment;

FIG. 28 is a diagram that illustrates the calculation of a secondcorrection coefficient according to the first embodiment;

FIG. 29 is a graph that illustrates the relation between the verticalcoordinate and the second correction coefficient according to the firstembodiment;

FIG. 30A is a diagram that illustrates an example of cutting out ofimage data, image data on a display element, and a projection imageaccording to the first embodiment in a case where the projection angleis 0°;

FIG. 30B is a diagram that illustrates an example of the cutting out ofthe image data, the image data on the display element, and theprojection image according to the first embodiment in a case where theprojection angle is 0°;

FIG. 30C is a diagram that illustrates an example of the cutting out ofthe image data, the image data on the display element, and theprojection image according to the first embodiment in a case where theprojection angle is 0°;

FIG. 30D is a diagram that illustrates an example of the cutting out ofthe image data, the image data on the display element, and theprojection image according to the first embodiment in a case where theprojection angle is 0°;

FIG. 31A is a diagram that illustrates an example of cutting out ofimage data, image data on a display element, and a projection imageaccording to the first embodiment in a case where the projection angleis greater than 0°, and the geometric distortion correction is notperformed;

FIG. 31B is a diagram that illustrates an example of the cutting out ofthe image data, the image data on the display element, and theprojection image according to the first embodiment in a case where theprojection angle is greater than 0°, and the geometric distortioncorrection is not performed;

FIG. 31C is a diagram that illustrates an example of the cutting out ofthe image data, the image data on the display element, and theprojection image according to the first embodiment in a case where theprojection angle is greater than 0°, and the geometric distortioncorrection is not performed;

FIG. 31D is a diagram that illustrates an example of the cutting out ofthe image data, the image data on the display element, and theprojection image according to the first embodiment in a case where theprojection angle is greater than 0°, and the geometric distortioncorrection is not performed;

FIG. 32A is a diagram that illustrates an example of cutting out ofimage data, image data on a display element, and a projection imageaccording to the first embodiment in a case where the projection angleis greater than 0°, and a conventional trapezoidal distortion correctionis performed;

FIG. 32B is a diagram that illustrates an example of the cutting out ofthe image data, the image data on the display element, and theprojection image according to the first embodiment in a case where theprojection angle is greater than 0°, and the conventional trapezoidaldistortion correction is performed;

FIG. 32C is a diagram that illustrates an example of the cutting out ofthe image data, the image data on the display element, and theprojection image according to the first embodiment in a case where theprojection angle is greater than 0°, and the conventional trapezoidaldistortion correction is performed;

FIG. 32D is a diagram that illustrates an example of the cutting out ofthe image data, the image data on the display element, and theprojection image according to the first embodiment in a case where theprojection angle is greater than 0°, and the conventional trapezoidaldistortion correction is performed;

FIG. 33A is a diagram that illustrates an example of cutting out ofimage data, image data on a display element, and a projection imageaccording to the first embodiment in a case where the projection angleis greater than 0°, and a geometric distortion correction according tothe first embodiment is performed;

FIG. 33B is a diagram that illustrates an example of the cutting out ofthe image data, the image data on the display element, and theprojection image according to the first embodiment in a case where theprojection angle is greater than 0°, and the geometric distortioncorrection according to the first embodiment is performed;

FIG. 33C is a diagram that illustrates an example of the cutting out ofthe image data, the image data on the display element, and theprojection image according to the first embodiment in a case where theprojection angle is greater than 0°, and the geometric distortioncorrection according to the first embodiment is performed;

FIG. 33D is a diagram that illustrates an example of the cutting out ofthe image data, the image data on the display element, and theprojection image according to the first embodiment in a case where theprojection angle is greater than 0°, and the geometric distortioncorrection according to the first embodiment is performed;

FIG. 34 is a flowchart that illustrates the sequence of an imageprojection process according to the first embodiment;

FIG. 35 is a flowchart that illustrates the sequence of an image datacutting out and geometric distortion correction process according to thefirst embodiment;

FIG. 36 is a flowchart that illustrates the sequence of an image datacutting out and geometric distortion correction process according to amodified example of the first embodiment;

FIG. 37A is a diagram that illustrates an example of cutting out ofimage data, image data on a display element, and a projection image in acase where the projection angle is greater than 0°, and a geometricdistortion correction according to a modified example of the firstembodiment is performed;

FIG. 37B is a diagram that illustrates an example of the cutting out ofthe image data, the image data on the display element, and theprojection image in a case where the projection angle is greater than0°, and the geometric distortion correction according to the modifiedexample of the first embodiment is performed;

FIG. 37C is a diagram that illustrates an example of the cutting out ofthe image data, the image data on the display element, and theprojection image in a case where the projection angle is greater than0°, and the geometric distortion correction according to the modifiedexample of the first embodiment is performed;

FIG. 37D is a diagram that illustrates an example of the cutting out ofthe image data, the image data on the display element, and theprojection image in a case where the projection angle is greater than0°, and the geometric distortion correction according to the modifiedexample of the first embodiment is performed;

FIG. 38 is a diagram that illustrates a change in a projection imageaccording to a change of the projection angle θ in a case where akeystone correction is not performed;

FIG. 39 is a diagram that illustrates an example of a case where atrapezoidal distortion correction is performed for a projection image inwhich a trapezoidal distortion is generated;

FIG. 40 is a diagram that illustrates an example of a change in thevertical-direction size of a projection image according to theprojection angle θ;

FIG. 41 is a diagram that illustrates a method of calculating the lengthof a shorter side of a projection image according to a secondembodiment;

FIG. 42 is a diagram that illustrates the method of calculating thelength of the shorter side of the projection image according to thesecond embodiment;

FIG. 43 is a block diagram that illustrates the configuration of anexample of a circuit unit and an optical engine unit according to thesecond embodiment;

FIG. 44 is a flowchart that illustrates the flow of an image projectionprocess performed by a projector device that can be applied to thesecond embodiment;

FIG. 45 is a flowchart that illustrates the flow of a keystonecorrection and a reduction process according to the second embodiment;

FIG. 46A is a diagram that illustrates the keystone correction and thereduction process according to the second embodiment more specifically;

FIG. 46B is a diagram that illustrates the keystone correction and thereduction process according to the second embodiment more specifically;

FIG. 47 is a flowchart that illustrates the flow of a keystonecorrection and a reduction process according to a modified example ofthe second embodiment;

FIG. 48A is a diagram that illustrates the keystone correction and thereduction process according to the modified example of the secondembodiment more specifically;

FIG. 48B is a diagram that illustrates the keystone correction and thereduction process according to the modified example of the secondembodiment more specifically;

FIG. 49 is a diagram that illustrates a first distance measurementmethod that can be applied to be common to the second embodiment and themodified example of the second embodiment;

FIG. 50 is a diagram that schematically illustrates a change in thedistance r with respect to the projection angle θ that can be applied tobe common to the second embodiment and the modified example of thesecond embodiment;

FIG. 51 is a diagram illustrating that the first distance measurementmethod can respond also to a case where a plurality of boundaries areincluded that can be applied to be common to the second embodiment andthe modified example of the second embodiment;

FIG. 52 is a diagram that illustrates an example, in which a pluralityof distance sensors are arranged in the drum unit, relating to the firstdistance measurement method that can be applied to be common to thesecond embodiment and the modified example of the second embodiment;

FIG. 53 is a diagram that illustrates a second distance measurementmethod that can be applied to be common to the second embodiment and themodified example of the second embodiment;

FIG. 54 is a diagram that illustrates a method of calculating aprojection angle for a boundary between a wall and a ceiling accordingto the second distance measurement method that can be applied to becommon to the second embodiment and the modified example of the secondembodiment;

FIG. 55 is a flowchart that illustrates the flow of an image projectionprocess performed by a projector device that can be applied to a thirdembodiment;

FIG. 56 is a block diagram that illustrates the configuration of anexample of a circuit unit and an optical engine unit of a projectordevice according to a fourth embodiment;

FIG. 57 is a block diagram that illustrates the configuration of anexample of an emission optical system according to the fourthembodiment;

FIG. 58 is a block diagram that illustrates the configuration of anexample of a lens control unit according to the fourth embodiment;

FIG. 59 is a diagram that schematically illustrates control of focusadjustment performed by a focus adjusting unit according to the fourthembodiment;

FIG. 60 is a flowchart that illustrates an example of a register controlmethod used by a determination unit according to the fourth embodiment;and

FIG. 61 is a flowchart that illustrates another example of a registercontrol method used by the determination unit according to the fourthembodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a projection device, an image correction method and acomputer-readable recording medium according to embodiments will bedescribed in detail with reference to the accompanying drawings.Specific numerical values, external configurations, and the likerepresented in the embodiments are merely examples for easyunderstanding of the present invention but are not for the purpose oflimiting the present invention unless otherwise mentioned. In addition,elements not directly relating to the present invention are notdescribed in detail and are not presented in the drawings.

Configuration Common to Embodiments

External Appearance of Projection Device

FIGS. 1A and 1B are schematic diagrams that illustrate an example of theexternal appearances of a projection device (projector device) 1 thatcan be applied to be common to embodiments. FIG. 1A is a perspectiveview of the projector device 1 viewed from a first face side on which anoperation unit is disposed, and FIG. 1B is a perspective view of theprojector device 1 viewed from a second face side that is a side facingthe operation unit. The projector device 1 includes a drum unit 10 and abase 20. The drum unit 10 is a rotor that is driven to be rotatable withrespect to the base 20. In addition, the base 20 includes a supportportion supporting the drum unit 10 to be rotatable and a circuit unitperforming various control operations such as rotation driving controlof the drum unit 10 and image processing control.

The drum unit 10 is supported to be rotatable by a rotation shaft, whichis not illustrated in the figure, disposed on the inner side of sideplate portions 21 a and 21 b that are parts of the base 20 and isconfigured by a bearing and the like. Inside the drum unit 10, a lightsource, a display element that modulates light emitted from the lightsource based on image data, a drive circuit that drives the displayelement, an optical engine unit that includes an optical systemprojecting the light modulated by the display element to the outside,and a cooling means configured by a fan and the like used for coolingthe light source and the like are disposed.

In the drum unit 10, window portions 11 and 13 are disposed. The windowportion 11 is disposed such that light projected from a projection lens12 of the optical system described above is emitted to the outside. Inthe window portion 13, a distance sensor deriving a distance up to aprojection medium, for example, using an infrared ray, an ultrasonicwave, or the like is disposed. In addition, the drum unit 10 includes anintake/exhaust hole 22 a that performs air in-taking/exhausting for heatrejection using a fan.

Inside the base 20, various substrates of the circuit unit, a powersupply unit, a drive unit used for driving the drum unit 10 to berotated, and the like are disposed. The rotary drive of the drum unit 10that is performed by this drive unit will be described later. On thefirst face of the base 20, an operation unit 14 used for inputtingvarious operations for controlling the projector device 1 and areception unit 15 that receives a signal transmitted by a user from aremote control commander not illustrated in the figure when theprojector device 1 is remotely controlled are disposed. The operationunit 14 includes various operators receiving user's operation inputs, adisplay unit used for displaying the state of the projector device 1,and the like.

On the first face side and the second face side of the base 20,intake/exhaust holes 16 a and 16 b are respectively disposed. Thus, evenin a case where the intake/exhaust hole 22 a of the drum unit 10 that isdriven to be rotated takes a posture toward the base 20 side, airin-taking or air exhaust can be performed so as not to decrease the heatrejection efficiency of the inside of the drum unit 10. In addition, anintake/exhaust hole 17 disposed on the side face of the casing performsair in-taking and air exhaust for heat rejection of the circuit unit.

Rotary Drive of Drum Unit

FIGS. 2A and 2B are diagrams that illustrate the rotary drive of thedrum unit 10, which can be applied to be common to the embodiments,performed by a drive unit 32 disposed in the base 20. FIG. 2A is adiagram that illustrates the configuration of a drum 30 in a state inwhich a cover and the like of the drum unit 10 are removed and the driveunit 32 disposed in the base 20. In the drum 30, a window portion 34corresponding to the window portion 11 described above and a windowportion 33 corresponding to the window portion 13 are disposed. The drum30 includes a rotation shaft 36 and is attached to a bearing 37 usingbearings disposed in support portions 31 a and 31 b to be driven torotate by the rotation shaft 36.

On one face of the drum 30, a gear 35 is disposed on the circumference.The drum 30 is driven to be rotated through the gear 35 by the driveunit 32 disposed in the support portion 31 b. Here, protrusions 46 a and46 b disposed in the inner circumference portion of the gear 35 aredisposed so as to detect a start point and an end point at the time ofthe rotating operation of the drum 30.

FIG. 2B is an enlarged diagram that illustrates the configuration of thedrum 30 and the drive unit 32 disposed in the base 20 in more detail.The drive unit 32 includes a motor 40 and a gear group including a wormgear 41 that is directly driven by the rotation shaft of the motor 40,gears 42 a and 42 b that transfer rotation according to the worm gear41, and a gear 43 that transfers the rotation transferred from the gear42 b to the gear 35 of the drum 30. By transferring the rotation of themotor 40 to the gear 35 using the gear group, the drum 30 can be rotatedin accordance with the rotation of the motor 40. As the motor 40, forexample, a stepping motor performing rotation control for eachpredetermined angle using a drive pulse may be used.

In addition, photo interrupters 51 a and 51 b are disposed towards thesupport portion 31 b. The photo interrupters 51 a and 51 b respectivelydetect the protrusions 46 a and 46 b disposed in the inner circumferenceportion of the gear 35. Output signals of the photo interrupters 51 aand 51 b are supplied to a rotation control unit 104 to be describedlater. In the embodiment, by detecting the protrusion 46 b using thephoto interrupter 51 a, the rotation control unit 104 determines thatthe posture of the drum 30 is a posture arriving at an end point of therotation operation. In addition, by detecting the protrusion 46 a usingthe photo interrupter 51 b, the rotation control unit 104 determinesthat the posture of the drum 30 is a posture arriving at a start pointof the rotation operation.

Hereinafter, a direction in which the drum 30 rotates from a position atwhich the protrusion 46 a is detected by the photo interrupter 51 b to aposition at which the protrusion 46 b is detected by the photointerrupter 51 a through a longer arc in the circumference of the drum30 will be represented as a forward direction. In other words, therotation angle of the drum 30 increases toward the forward direction.

In addition, the photo interrupters 51 a and 51 b and the protrusions 46a and 46 b are arranged such that an angle formed with the rotationshaft 36 is 270° between the detection position at which the photointerrupter 51 b detects the protrusion 46 a and the detection positionat which the photo interrupter 51 a detects the protrusion 46 b.

For example, in a case where a stepping motor is used as the motor 40,by specifying the posture of the drum 30 based on timing at which theprotrusion 46 a is detected by the photo interrupter 51 b and the numberof drive pulses used for driving the motor 40, a projection angleaccording to the projection lens 12 can be acquired.

Here, the motor 40 is not limited to the stepping motor but, forexample, a DC motor may be used. In such a case, for example, asillustrated in FIG. 2B, a code wheel 44 rotating together with the gear43 on the same shaft as that of the gear 43 is disposed, and photoreflectors 50 a and 50 b are disposed in the support portion 31 b,whereby a rotary encoder is configured.

In the code wheel 44, for example, a transmission portion 45 a and areflection portion 45 b having phases changing in the radial directionare disposed. By receiving reflected light having each phase from thecode wheel 44 using the photo reflectors 50 a and 50 b, the rotationspeed and the rotation direction of the gear 43 can be detected. Then,based on the rotation speed and the rotation direction of the gear 43that have been detected, the rotation speed and the rotation directionof the drum 30 are derived. Based on the rotation speed and the rotationdirection of the drum 30 that have been derived and a result of thedetection of the protrusion 46 b that is performed by the photointerrupter 51 a, the posture of the drum 30 is specified, whereby theprojection angle according to the projection lens 12 can be acquired.

In the configuration as described above, a state in which the projectiondirection according to the projection lens 12 is in the verticaldirection, and the projection lens 12 is completely hidden by the base20 will be referred to as a housed state (or housing posture). FIG. 3 isa schematic diagram that illustrates each posture of the drum unit 10.In FIG. 3, State 500 illustrates the appearance of the drum unit 10 thatis in the housed state. In the embodiment, the protrusion 46 a isdetected by the photo interrupter 51 b in the housed state, and it isdetermined that the drum 30 arrives at the start point of the rotationoperation by the rotation control unit 104 to be described later.

Hereinafter, unless otherwise mentioned, the “direction of the drum unit10” and the “angle of the drum unit 10” have the same meanings as the“projection direction according to the projection lens 12” and the“projection angle according to the projection lens 12”.

For example, when the projector device 1 is started up, the drive unit32 starts to rotate the drum unit 10 such that the projection directionaccording to the projection lens 12 faces the above-described firstface. Thereafter, the drum unit 10, for example, is assumed to rotate upto a position at which the direction of the drum unit 10, in otherwords, the projection direction according to the projection lens 12 ishorizontal on the first face side and temporarily stop. The projectionangle of the projection lens 12 of a case where the projection directionaccording to the projection lens 12 is horizontal on the first face sideis defined as a projection angle of 0°. In FIG. 3, State 501 illustratesthe appearance of the posture of the drum unit 10 (projection lens 12)when the projection angle is 0°. Hereinafter, the posture of the drumunit 10 (projection lens 12) at which the projection angle is θ with theposture having a projection angle of 0° used as the reference will bereferred to as a θ posture. In addition, the state of the posture havinga projection angle of 0° (in other words, a 0° posture) will be referredto as an initial state.

For example, at the 0° posture, it is assumed that image data is input,and the light source is turned on. In the drum unit 10, light emittedfrom the light source is modulated based on the image data by thedisplay element driven by the drive circuit and is incident to theoptical system. Then, the light modulated based on the image data isprojected from the projection lens 12 in a horizontal direction and isemitted to the projection face of the projection medium such as a screenor a wall face.

By operating the operation unit 14 and the like, the user can rotate thedrum unit 10 around the rotation shaft 36 as its center while projectionis performed from the projection lens 12 based on the image data. Forexample, by configuring the rotation angle to be 90° (90° posture) byrotating the drum unit 10 from the 0° posture in the forward direction,light emitted from the projection lens 12 can be projected verticallyupwardly with respect to the bottom face of the base 20. In FIG. 3,State 502 illustrates the appearance of the drum unit 10 at the posturehaving a projection angle θ of 90°, in other words, a 90° posture.

The drum unit 10 can be rotated further in the forward direction fromthe 90° posture. In such a case, the projection direction of theprojection lens 12 changes from the vertically upward direction withrespect to the bottom face of the base 20 to the direction of the secondface side. In FIG. 3, State 503 illustrates an appearance acquired whena posture having a projection angle θ of 180°, in other words, a 180°posture is formed as the drum unit 10 further rotates in the forwarddirection from the 90° posture of State 502. In the projector device 1according to the embodiment, the protrusion 46 b is detected by thephoto interrupter 51 a in this 180° posture, and it is determined thatthe drum has arrived at the end point of the rotation operation of thedrum 30 by the rotation control unit 104 to be described later.

As will be described in detail later, the projector device 1 accordingto this embodiment rotates the drum unit 10, for example, as illustratedin States 501 to 503 with projection of an image being performed,thereby changing (moving) a projection area of image data in accordancewith the projection angle according to the projection lens 12.Accordingly, changes in the content of a projected image and theprojection position of the projected image in the projection medium andchanges in the content and the position of the image area cut out as animage to be projected from the whole image area relating to input imagedata can be associated with each other. Accordingly, a user canintuitively perceive an area which is projected out of the whole imagearea relating to the input image data based on the position of theprojected image in the projection medium and intuitively perform anoperation of changing the content of the projected image.

In addition, the optical system includes an optical zoom mechanism andcan enlarge or reduce the size at the time of projecting a projectionimage to the projection medium by operating the operation unit 14.Hereinafter, the enlarging or reducing of the size at the time ofprojecting the projection image to the projection medium according tothe optical system may be simply referred to as “zooming”. For example,in a case where the optical system performs zooming, the projectionimage is enlarged or reduced with the optical axis of the optical systemat the time point of performing zooming as its center.

When the user ends the projection of the projection image using theprojector device 1 and stops the projector device 1 by performing anoperation for instructing the operation unit 14 to stop the projectordevice 1, first, rotation control is performed such that the drum unit10 is returned to be in the housed state. When the drum unit 10 ispositioned toward the vertical direction, and the return of the drumunit 10 into the housed state is detected, the light source is turnedoff, and, after a predetermined time required for cooling the lightsource, the power is turned off. By turning the power off after the drumunit 10 is positioned toward the vertical direction, the projection lens12 can be prevented from getting dirty when the projection lens is notused.

Functional Configuration of Projector Device

Next, a configuration for realizing each function or operation of theprojector device 1 according to each embodiment, as described above,will be described. FIG. 4 is a block diagram that illustrates thefunctional configuration of the projector device 1.

As illustrated in FIG. 4, the projector device 1 mainly includes: anoptical engine unit 110, an image processing/controlling unit 90; adrive system control unit 91; an overall control unit 120; and anoperation unit 14. Here, the optical engine unit 110 is disposed insidethe drum unit 10. In addition, the image processing/controlling unit 90,the drive system control unit 91, and the overall control unit 120 aremounted on the substrate of a base 20 as a circuit unit.

The optical engine unit 110 includes a light source 111, a displayelement 114, and a projection lens 12. The light source 111, forexample, includes three LEDs (Light Emitting Diode) respectivelyemitting red (R) light, green (G) light, and blue (B) light. Luminousfluxes of colors RGB that are emitted from the light source 111irradiate the display element 114 through an optical system notillustrated in the figure.

In description presented below, the display element 114 is assumed to bea transmission-type liquid crystal display device and, for example, tohave a size of horizontal 1280 pixels×vertical 720 pixels. However, thesize of the display element 114 is not limited to this example. Thedisplay element 114 is driven by a drive circuit not illustrated in thefigure and modulates luminous fluxes of the colors RGB based on imagedata and emits the modulated luminous fluxes. The luminous fluxes of thecolors RGB that are emitted from the display element 114 and aremodulated based on the image data are incident to the projection lens 12through the optical system and are projected to the outside of theprojector device 1.

In addition, the display element 114, for example, may be configured bya reflection-type liquid crystal display device using LCOS (LiquidCrystal on Silicon) or a DMD (Digital Micromirror Device). In such acase, the projector device is configured by an optical system and adrive circuit that correspond to the used display element.

The projection lens 12 includes a plurality of lenses that are combinedtogether and a lens driving unit that drives the lenses according to acontrol signal. For example, the lens driving unit drives a lensincluded in the projection lens 12 based on a result of distancemeasurement that is acquired based on an output signal output from adistance sensor disposed in the window portion 13, thereby performingfocus control. In addition, the lens driving unit changes the view angleby driving the lens in accordance with a zoom instruction supplied froma view angle control unit 106 to be described later included in thedrive system control unit 91, thereby controlling the optical zoom.

As described above, the optical engine unit 110 is disposed inside thedrum unit 10 that can be rotated by 360° by a rotation mechanism unit105. The rotation mechanism unit 105 includes the drive unit 32 and thegear 35 that is a configuration of the drum unit 10 side described withreference to FIG. 2 and rotates the drum unit 10 in a predeterminedmanner using the rotation of the motor 40. In other words, theprojection direction of the projection lens 12 is changed by therotation mechanism unit 105.

In the circuit unit of the projector device 1, the overall control unit120, for example, includes: a central processing unit (CPU), read onlymemory (ROM); and random access memory (RAM). In the overall controlunit 120, the CPU performs overall control of various processes of theprojector device 1 such as projecting a projection image, changing aprojection angle, and cutting out of an image according to a programstored in the ROM in advance by using the RAM as a work memory.

For example, the overall control unit 120 controls each unit of theprojector device 1 according to a program based on a control signalsupplied from the operation unit 14 according to a user's operation.Accordingly, the projector device 1 can be operated according to auser's operation. However, the control operation is not limited thereto.Thus, the overall control unit 120, for example, may control each unitof the projector device 1 according to a script input from a data inputunit not illustrated in the figure. In this way, the operation of theprojector device 1 can be automatically controlled.

Image data 92 of a still image or a moving image is input to theprojector device 1 and is supplied to the image processing/controllingunit 90. The image processing/controlling unit 90 stores the suppliedimage data 92 in an image memory 101. The image memory 101 stores theimage data 92 in units of images. In other words, for each still imagein a case where the image data 92 is still image data and for each frameimage configuring moving image data in a case where the image data 92 isthe moving image data, the image memory 101 stores corresponding data.The image memory 101, for example, in compliance with the standards ofdigital high vision broadcasting, can store one or a plurality of frameimages of 1920 pixels and 1080 pixels.

In addition, it is preferable that the size of the image data 92 isshaped in advance into a size corresponding to the storage unit of theimage data in the image memory 101, and resultant input image data isinput to the projector device 1. In this example, the size of the inputimage data 92 is shaped into 1920 pixels×1080 pixels, and resultantimage is input to the projector device 1. However, the configuration isnot limited thereto, but, in the projector device 1, the imageprocessing/controlling unit 90 may perform an image shaping process thatshapes the input image data 92 input with an arbitrary size into imagedata of a size of 1920 pixels and 1080 pixels and then store the imagedata into the image memory 101.

The image processing/controlling unit 90 includes an image cutting-outunit that designates an area from which image data is cut out for thewhole area of a frame image relating to the image data stored in theimage memory 101. The image processing/controlling unit 90 cuts out adesignated image area from the image data stored in the image memory 101by using the image cutting-out unit and performs image processing forthe cut-out image data.

For example, the image processing/controlling unit 90 performs a sizeconverting process for image data acquired by cutting out the designatedarea from the image data stored in the image memory 101 such that thesize coincides with the size of the display element 114. For example,the image processing/controlling unit 90 may perform the size convertingprocess for the image data by using a general linear transformationprocess. In such a case, the size converting process may be omitted in acase where the size of the image data coincides with the size of thedisplay element 114.

Other than the size converting process, the image processing/controllingunit 90 may perform various kinds of image processing. For example, theimage processing/controlling unit 90 may perform a process relating to aso-called keystone correction (geometric distortion correction) for aprojected image.

In addition, by performing interpolation (over sampling) with the aspectratio of the image being maintained to be constant, the imageprocessing/controlling unit 90 may enlarge a part or the whole of theimage through an interpolation filter having a predeterminedcharacteristic, in order to extract an aliasing distortion, by thinningout (sub sampling) the image through a low pass filter according to areduction rate, the image processing/controlling unit 90 may reduce apart or the whole of the image, or the image processing/controlling unit90 may maintain the size without causing the image to pass through afilter.

Furthermore, when an image is projected in an inclined direction, inorder to prevent an out-of-focus image from being blurred in aperipheral portion, the image processing/controlling unit 90 may enhancethe edge of a blurred image portion that is projected by performing anedge enhancement process using an operator (or applying one-dimensionalfilters in horizontal and vertical directions) such as Laplacian.

In addition, in order to prevent the brightness of the whole screen fromchanging due to a change in the projection size (area) according to thekeystone correction described above or the like, the imageprocessing/controlling unit 90 may perform adaptive luminance adjustmentso as to maintain uniform brightness. In a case where a peripheryportion of a projected image texture includes a diagonal line, in ordernot to allow an edge jag to be visually noticed, the imageprocessing/controlling unit 90 may prevent the diagonal line from beingobserved as a jagged line by mixing a local halftone or applying a locallow pass filter to shade off the edge jag.

The image data output from the image processing/controlling unit 90 issupplied to the display element 114. Actually, this image data issupplied to the drive circuit that drives the display element 114. Thedrive circuit drives the display element 114 based on the supplied imagedata.

The drive system control unit 91 includes: the rotation control unit 104and the view angle control unit 106 described above. The rotationcontrol unit 104, for example, receives an instruction according to auser's operation for the operation unit 14 and instructs the rotationmechanism unit 105 according to the instruction according to the user'soperation. The rotation mechanism unit 105 includes the drive unit 32and the photo interrupters 51 a and 51 b described above. The rotationmechanism unit 105 controls the drive unit 32 according to aninstruction supplied from the rotation control unit 104 and controls therotation operation of the drum unit 10 (drum 30). For example, therotation mechanism unit 105 generates a drive pulse according to aninstruction supplied from the rotation control unit 104, thereby drivinga motor 40 that is, for example, a stepping motor. The rotation controlunit 104, for example, generates a drive pulse in synchronization with avertical synchronization signal VD supplied from a timing generator notillustrated in the figure.

Meanwhile, the outputs of the photo interrupters 51 a and 51 b describedabove and a drive pulse used for driving the motor 40 are supplied fromthe rotation mechanism unit 105 to the rotation control unit 104. Therotation control unit 104, for example, includes a counter and countsthe pulse number of drive pulses. The rotation control unit 104 acquiresthe timing of detection of the protrusion 46 a based on the output ofthe photo interrupter 51 b and resets the pulse number counted by thecounter at the timing of the detection of the protrusion 46 a. Therotation control unit 104, based on the pulse number counted by thecounter, can sequentially acquire the angle of the drum unit 10 (drum30), thereby acquiring the posture (in other words, the projection angleof the projection lens 12) of the drum unit 10. The projection angle ofthe projection lens 12 is supplied to the drive system control unit 91.In this way, in a case where the projection direction of the projectionlens 12 is changed, the rotation control unit 104 can derive an anglebetween a projection direction before change and a projection directionafter the change.

In the drive system control unit 91, the view angle control unit 106,for example, through an input control unit 119 and gives a zoominstruction based on an instruction according to a user operation forthe operation unit 14, in other words, an instruction for changing theview angle to the projection lens 12 based on the instruction accordingto the user operation. The lens driving unit of the projection lens 12drives the lens based on the zoom instruction, thereby performing zoomcontrol. The view angle control unit 106 supplies the zoom instructionand information of a view angle derived based on a zoom magnificationrelating to the zoom instruction to the image processing/controllingunit 90.

The image processing/controlling unit 90 designates an image cut-outarea for which image data stored in the image memory 101 is cut outbased on the information relating to the angle supplied from therotation control unit 104 and the information relating to the view anglesupplied from the view angle control unit 106. At this time, the imageprocessing/controlling unit 90 designates a cut-out area of the imagedata based on a line position according to an angle between projectiondirections of the projection lens 12 before and after the change.

In the description presented above, while the imageprocessing/controlling unit 90 and the drive system control unit 91 havebeen described as separate hardware, the configuration is not limited tosuch an example. For example, each of the units may be realized by amodule of a program that operates on the CPU included in the overallcontrol unit 120.

Cutting Out Process of Image Data

Next, a cutting out process of image data stored in the image memory 101that is performed by the image processing/controlling unit 90 accordingto each embodiment will be described. FIG. 5 is a conceptual diagramthat illustrates the cutting out process of image data, which is storedin the image memory 101, according to each embodiment. An example ofcutting out image data 141 of the cut-out area designated from imagedata 140 stored in the image memory 101 will be described with referenceto a left diagram in FIG. 5.

In addition, in description presented below with reference to FIGS. 6 to9, for simple description, a case where a geometric distortioncorrection is not performed for the image data and a case where thepixel size of the image data in the horizontal direction coincides withthe pixel size of the display element 114 in the horizontal directionwill be premised.

The image processing/controlling unit 90 designates addresses of linesq₀ and q₁ in the vertical direction and designates addresses of pixelsp₀ and p₁ in the horizontal direction as a cut-out area of the imagedata 140 of Q lines×P pixels stored in the image memory 101. The imageprocessing/controlling unit 90 reads lines within the range of the linesq₀ and q₁ over the pixels p₀ and p₁ from the image memory 101 inaccordance with the designation of the addresses. At this time, as thesequence of reading, for example, it is assumed that the lines are readfrom the upper end toward the lower end of the image, and the pixels areread from the left end toward the right end of the image. The accesscontrol for the image memory 101 will be described in detail later.

The image processing/controlling unit 90 performs image processing forthe image data 141 of the range of the lines q₀ and q₁ and the pixels p₀and p₁ that has been read from the image memory 101. The imageprocessing/controlling unit 90 performs a size conversion process inwhich the size of an image according to the supplied image data 141 isadjusted to the size of the display element 114. As an example, in acase where the size of the display element 114 is V lines×H pixels, amaximum multiplication m satisfying both Equations (1) and (2) asrepresented below is acquired. Then, the image processing/controllingunit 90 enlarges the image data 141 with this multiplication m and, asillustrated in a diagram disposed on the right side in FIG. 5 as anexample, size-converted image data 141′ is acquired.

m×(p ₁ −p ₀)≦H  (1)

m×(q ₁ −q ₀)≦V  (2)

Next, the designation (update) of a cut-out area according to theprojection angle according to each embodiment will be described. FIG. 6illustrates an example of designation of a cut-out area of a case wherethe drum unit 10 is at the 0° posture, in other words, in a case wherethe projection angle is 0°.

In FIG. 5 described above, a case has been described as an example inwhich the image data 141 of the range of the pixels p₀ and p₁ that is apartial range of pixels of one line of the image data 140 of Q lines×Ppixels stored in the image memory 101 is cut out. Also in examplesillustrated in FIGS. 6 to 8, actually, pixels of a partial range of oneline of the image data 140 stored in the image memory 101 may be cutout. However, in order to simplify the description of the designation(update) of a cut-out area according to the projection angle, theexamples represented in FIGS. 6 to 8 illustrated below, all the pixelsof one line are assumed to be cut out.

In the projector device (PJ) 1, a projection position of a case where animage 131 ₀ is projected with a projection angle of 0° onto a projectionface 130 that is a projection medium such as a screen by using aprojection lens 12 having a view angle α is assumed to be a positionPos₀ corresponding to a center of luminous flux of light projected fromthe projection lens 12. In addition, at the projection angle of 0°, animage according to image data from the S-th line that is the lower endof an area designated in advance to the L-th line is assumed to beprojected such that the image data stored in the image memory 101 isprojected at the posture of a projection angle of 0°. In the area formedby lines of the S-th line to the L-th line, lines corresponding to theline number ln are included. In addition, a value representing a lineposition such as the S-th line or the L-th line, for example, is a valueincreasing from the lower end toward the upper end of the displayelement 114 with the line positioned at the lower end of the displayelement 114 set as the 0-th line.

Here, the line number ln is the number of lines of a maximal effectivearea of the display element 114. In addition, the view angle α is anangle for viewing a projection image in the vertical direction from theprojection lens 12 in a case where the image is projected when aneffective area in the vertical direction, in which the display iseffective in the display element 114, has a maximum value, in otherwords, in a case where an image of the line number in is projected.

The view angle α and the effective area of the display element 114 willbe described using a more specific example. The display element 114 isassumed to have a size of 800 lines in the vertical direction. Forexample, in a case where the size of the projection image data is 800lines in the vertical direction, and projection image data is projectedusing all the lines of the display element 114, the effective area ofthe display element 114 in the vertical direction has a maximum value of800 lines (=line number 1 n). In this case, the view angle α is an anglefor viewing 1st to 800th lines of the projection image from theprojection lens 12.

In addition, a case may be also considered in which the size ofprojection image data in the vertical direction is 600 lines, and theprojection image data is projected using only 600 lines out of 800 lines(=line number 1 n) of the display element 114. In such a case, theeffective area of the display element 114 in the vertical direction is600 lines. In this case, only a portion of the effective area accordingto the projection image data with respect to a maximal value of theeffective area of the view angle α is projected.

The image processing/controlling unit 90 performs a process of cuttingout and reading the S-th line to L-th line of the image data 140 storedin the image memory 101. Here, in the horizontal direction, all theimage data 140 of the left end to the right end is read. The imageprocessing/controlling unit 90 sets an area of the S-th line to the L-thline of the image data 140 as a cut-out area and reads the image data141 of the set cut-out area. In the example illustrated in FIG. 6, ontothe projection face 130, an image 131 ₀ according to image data 141 ₀ ofthe line number in from the S-th line to the L-th line of the image data140 is projected. In such a case, an image according to image data 142of an area relating to the L-th line to the upper-end line out of thewhole area of the image data 140 is not projected.

Next, a case will be described in which the drum unit 10 is rotated, forexample, according to a user operation for the operation unit 14, andthe projection angle of the projection lens 12 becomes an angle θ. Ineach embodiment, in a case where the drum unit 10 is rotated, and theprojection angle according to the projection lens 12 is changed, thecut-out area from the image memory 101 of the image data 140 is changedin accordance with the projection angle θ.

The setting of a cut-out area for the projection angle θ will bedescribed more specifically with reference to FIG. 7. For example, acase will be considered in which the drum unit 10 is rotated in theforward direction from a projection position of the 0° posture accordingto the projection lens 12, and the projection angle of the projectionlens 12 becomes an angle θ (>0°). In such a case, the projectionposition for the projection face 130 moves to a projection position Pos₁that is located on the upper side of a projection position Pos₀corresponding to a projection angle of 0°. At this time, the imageprocessing/controlling unit 90 designates a cut-out area for the imagedata 140 stored in the image memory 101 based on the following Equations(3) and (4). Equation (3) represents an R_(S)-th line located at thelower end of the cut-out area, and Equation (4) represents an R_(L)-thline located at the upper end of the cut-out area.

R _(S)=0×(ln/α)+S  (3)

R _(L)=0×(ln/α)+S+ln  (4)

In Equations (3) and (4), a value ln represents the number of lines (forexample, the number of lines of the display element 114) included withinthe projection area. In addition, a value α represents a view angle ofthe projection lens 12, and a value S represents a position of a linelocated at the lower end of the cut-out area at the 0° posture describedwith reference to FIG. 6.

In Equations (3) and (4), (ln/α) represents the concept of the number oflines (including a concept of an approximately averaged number of lineschanging in accordance with the shape of the projection face) per unitview angle of a case where the view angle α projects the line number ln.Accordingly, θ×(ln/α) represents the number of lines corresponding tothe projection angle θ according to the projection lens 12 in theprojector device 1. This means that, when the projection angle changesby an angle Δθ, the position of the projection image is moved by adistance corresponding to the number of lines {Δθ×(ln/α)} in theprojection image. Accordingly, Equations (3) and (4) respectivelyrepresent the positions of lines located at the lower end and the upperend of the image data 140 in the projection image of a case where theprojection angle is the angle θ. This corresponds to a read address forthe image data 140 on the image memory 101 at the projection angle θ.

In this way, in each embodiment, an address at the time of reading theimage data 140 from the image memory 101 is designated in accordancewith the projection angle θ. Accordingly, for example, in the exampleillustrated in FIG. 7, image data 141 ₁ of the image data 140 that islocated at a position corresponding to the projection angle θ is readfrom the image memory 101, and an image 131 ₁ relating to the read imagedata 141 ₁ is projected to the projection position Pos₁ corresponding tothe projection angle θ of the projection face 130.

Thus, according to each embodiment, in a case where the image data 140having a size larger than the size of the display element 114 isprojected, a correspondence relation between the position within theprojected image and the position within the image data is maintained. Inaddition, since the projection angle θ is acquired based on a drivepulse of the motor 40 used for driving the drum 30 to be rotated, theprojection angle θ can be acquired in a state in which there issubstantially no delay with respect to the rotation of the drum unit 10,and the projection angle θ can be acquired without being influenced bythe projection image or the surrounding environment.

Next, the setting of a cut-out area of a case where optical zoomingaccording to the projection lens 12 is performed will be described. Asdescribed above, in the case of the projector device 1, the view angle αof the projection lens 12 is increased or decreased by driving the lensdriving unit, whereby optical zooming is performed. An increase in theview angle according to the optical zooming is assumed to be an angle Δ,and the view angle of the projection lens 12 after the optical zoomingis assumed to be a view angle (α+Δ).

In such a case, even when the view angle is increased according to theoptical zooming, the cut-out area for the image memory 101 does notchange. In other words, the number of lines included in a projectionimage according to the view angle α before the optical zooming and thenumber of lines included in a projection image according to the viewangle (α+Δ) after the optical zooming are the same. Accordingly, afterthe optical zooming, the number of lines included per unit angle ischanged from that before the optical zooming.

The designation of a cut-out area of a case where optical zooming isperformed will be described more specifically with reference to FIG. 8.In the example illustrated in FIG. 8, optical zooming is performed inwhich the view angle α is increased by an amount corresponding to theview angle Δ in the state of the projection angle θ. By performing theoptical zooming, for example, a projection image projected onto theprojection face 130, as illustrated as an image 131 ₂, is enlarged by anamount corresponding to the view angle Δ with respect to that of a casewhere the optical zooming is not performed with the center (theprojection position Pos₂) of the luminous fluxes of light projected tothe projection lens 12.

In a case where optical zooming corresponding to the view angle Δ isperformed, when the number of lines designated as a cut-out area for theimage data 140 is ln, the number of lines included per unit angle isrepresented by {ln/(α+Δ)}. Accordingly, the cut-out area for the imagedata 140 is designated based on the following Equations (5) and (6). Themeaning of each variable in Equations (5) and (6) is common to that inEquations (3) and (4) described above.

R _(S)=0×{ln/(α+Δ)}+S  (5)

R _(L)=0×{ln/(α+Δ)}+S+ln  (6)

Image data 141 ₂ of an area represented in Equations (5) and (6) is readfrom the image data 140, and an image 131 ₂ relating to the read imagedata 141 ₂ is projected to a projection position Pos₂ of the projectionface 130 by the projection lens 12.

In this way, in a case where optical zooming is performed, the number oflines included per unit angle is changed with respect to a case wherethe optical zooming is not performed, and the amount of change in thenumber of lines with respect to a change in the projection angle θ isdifferent from that of a case where the optical zooming is notperformed. This is a state in which a gain corresponding to the viewangle Δ increased according to the optical zooming is changed in thedesignation of a read address according to the projection angle θ forthe image memory 101.

In this embodiment, an address at the time of reading the image data 140from the image memory 101 is designated in accordance with theprojection angle θ and the view angle α of the projection lens 12. Inthis way, even in a case where optical zooming is performed, the addressof the image data 141 ₂ to be projected can be appropriately designatedfor the memory 101. Accordingly, even in a case where the opticalzooming is performed, in a case where the image data 140 of a sizelarger than the size of the display element 114 is projected, acorrespondence relation between the position within the projected imageand the position within the image data is maintained.

Next, a case will be described with reference to FIG. 9 in which anoffset is given to the projection position of the image. When theprojector device 1 is used, it cannot be determined that the 0° posture(projection angle 0°) is necessarily the lowest end of the projectionposition. For example, as illustrated in FIG. 9, a case may beconsidered in which a projection position Pos₃ according to apredetermined projection angle θ_(ofst) is set as the projectionposition located at the lowest end. In such a case, the image 131 ₃according to the image data 141 ₃ is projected to a position shifted tothe upper side by a height corresponding to the projection angleθ_(ofst) compared to a case where the offset is not given. Theprojection angle θ at the time of projecting an image having a linelocated at the lowest end of the image data 140 as its lowest end is setas the offset angle θ_(ofst) according to the offset.

In such a case, for example, a case may be considered in which theoffset angle θ_(ofst) is regarded as the projection angle 0°, and acut-out area for the memory 101 is designated. By applying Equations (3)and (4) described above, the following Equations (7) and (8) are formed.The meaning of each variable in Equations (7) and (8) is common to thatin Equations (3) and (4) described above.

R _(S)=(θ−θ_(ofst))×(ln/α)+S  (7)

R _(L)=(θ−θ_(ofst))×(ln/α)+S+ln  (8)

The image data 141 ₃ of the area represented in Equations (7) and (8) isread from the image data 140, and the image 131 ₃ relating to the readimage data 141 ₃ is projected to the projection position Pos₃ of theprojection face 130 by the projection lens 12.

Memory Control

Next, access control of the image memory 101 will be described. In theimage data, for each vertical synchronization signal VD, pixels aresequentially transmitted from the left end toward the right end of animage for each line in the horizontal direction, and lines aresequentially transmitted from upper end toward the lower end of theimage. Hereinafter, a case will be described as an example in which theimage data has a size of horizontal 1920 pixels×vertical 1080 pixels(lines) corresponding to the digital high vision standard.

Hereinafter, an example of the access control of a case where the imagememory 101 includes four memory areas for which the access control canbe independently performed will be described. In other words, asillustrated in FIG. 10, in the image memory 101, areas of memories 101Y₁and 101Y₂ used for writing and reading image data with a size ofhorizontal 1920 pixels and vertical 1080 pixels (line) and areas ofmemories 101T₁ and 101T₂ used for writing and reading image data with asize of horizontal 1080 pixels×vertical 1920 pixels (lines) arearranged. Hereinafter, the areas of memories 101Y₁, 101Y₂, 101T₁, and101T₂ will be described as memories Y₁, Y₂, T₁, and T₂.

FIG. 11 is an example of a timing diagram that illustrates accesscontrol of the image memory 101 using the image processing/controllingunit 90 according to each embodiment. In FIG. 11, Chart 210 representsthe projection angle θ of the projection lens 12, and Chart 211represents the vertical synchronization signal VD. In addition, Chart212 represents input timings of image data D₁, D₂, and . . . input tothe image processing/controlling unit 90, and Charts 213 to 216represent examples of accesses to the memories Y₁, Y₂, T₁, and T₂ fromthe image processing/controlling unit 90. In addition, in Charts 213 to216, each block to which “R” is attached represents reading, and eachblock to which “W” is attached represents writing.

For every vertical synchronization signal VD, image data D₁, D₂, D₃, D₄,D₅, D₆, . . . each having an image size of 1920 pixels×1080 lines areinput to the image processing/controlling unit 90. Each of the imagedata D₁, D₂, . . . is synchronized with the vertical synchronizationsignal VD and is input after the vertical synchronization signal VD. Inaddition, the projection angles of the projection lens 12 correspondingto the vertical synchronization signals VD are denoted as projectionangles θ₁, θ₂, θ₃, θ₄, θ₅, θ₆, . . . . The projection angle θ isacquired for every vertical synchronization signal VD as above.

First, the image data D₁ is input to the image processing/controllingunit 90. As described above, the projector device 1 according to eachembodiment changes the projection angle θ according to the projectionlens 12 by rotating the drum unit 10 so as to move the projectionposition of the projection image and designates a read position for theimage data in accordance with the projection angle θ. Accordingly, it ispreferable that the image data is longer in the vertical direction.Generally, image data frequently has a horizontal-direction size longerthan a vertical-direction size. Thus, for example, it may be consideredfor a user to rotate the camera by 90° in an imaging process and inputimage data acquired by the imaging process to the projector device 1.

In other words, an image according to the image data D₁, D₂, . . . inputto the image processing/controlling unit 90, similar to an image 160illustrated as an image in FIG. 12A, is an image facing the sideacquired by rotating a right-direction image by 90° that is determinedbased on the content of the image.

The image processing/controlling unit 90 writes the input image data D₁,first, into the memory Y₁ at timing WD₁ corresponding to the inputtiming of the image data D₁ (timing WD₁ illustrated in Chart 213). Theimage processing/controlling unit 90 writes the image data D₁ into thememory Y₁, as illustrated on the left side of FIG. 12B, in the sequenceof lines toward the horizontal direction. On the right side of FIG. 12B,an image 161 according to the image data D₁ written into the memory Y₁as such is illustrated as an image. The image data D₁ is written intothe memory Y₁ as the image 161 that is the same as the input image 160.

The image processing/controlling unit 90, as illustrated in FIG. 12C,reads the image data D₁ written into the memory Y₁ from the memory Y₁ attiming RD₁ that is the same as the timing of start of a next verticalsynchronization signal VD after the vertical synchronization signal VDfor writing the image data D₁ (timing RD₁ illustrated in Chart 213).

At this time, the image processing/controlling unit 90 sequentiallyreads the image data D₁ in the vertical direction over the lines foreach pixel with a pixel positioned on the lower left corner of the imagebeing set as a reading start pixel. When pixels positioned at the upperend of the image are read, next, pixels are read in the verticaldirection with a pixel positioned on the right side neighboring to thepixel positioned at the reading start pixel of the vertical directionbeing set as a reading start position. This operation is repeated untilthe reading of a pixel positioned on the upper right corner of the imageis completed.

In other words, the image processing/controlling unit 90 sequentiallyreads the image data D₁ from the memory Y₁ for each line in the verticaldirection from the left end toward the right end of the image for eachpixel with the line direction being set as the vertical direction fromthe lower end toward the upper end of the image.

The image processing/controlling unit 90 sequentially writes the pixelsof the image data D₁ read from the memory Y₁ in this way, as illustratedon the left side in FIG. 13A, into the memory T₁ toward the linedirection for each pixel (timing WD₁ illustrated in Chart 214). In otherwords, for example, every time when one pixel is read from the memoryY₁, the image processing/controlling unit 90 writes one pixel that hasbeen read into the memory T₁.

On the right side in FIG. 13A, the image 162 according to the image dataD₁ written into the memory T₁ in this way is illustrated. The image dataD₁ is written into the memory T₁ with a size of horizontal 1080pixels×vertical 1920 pixels (lines) and is the image 162 acquired byrotating the input image 160 by 90° in the clockwise direction andinterchanging the horizontal direction and the vertical direction.

The image processing/controlling unit 90 designates an address of thedesignated cut-out area to the memory T₁ and reads image data of thearea designated as the cut-out area from the memory T₁. The timing ofthis reading process, as represented by timing RD₁ in Chart 214, isdelayed from the timing at which the image data D₁ is input to the imageprocessing/controlling unit 90 by two vertical synchronization signalsVD.

The projector device 1 according to each embodiment, as described above,moves the projection position of the projection image by rotating thedrum unit 10 so as to change the projection angle θ according to theprojection lens 12 and designates a reading position for image data inaccordance with the projection angle θ. For example, the image data D₁is input to the image processing/controlling unit 90 at the timing ofthe projection angle θ₁. The projection angle θ at the timing when animage according to the image data D₁ is actually projected may bechanged from the projection angle θ₁ to a projection angle θ₃ differentfrom the projection angle θ₁.

Accordingly, the cut-out area at the time of reading the image data D₁from the memory T₁ is read from a range that is larger than the area ofimage data corresponding to the projected image in consideration of achange in the projection angle θ.

The description will be presented more specifically with reference toFIG. 13B. The left side in FIG. 13B illustrates an image 163 accordingto the image data D₁ stored in the memory T₁. In this image 163, an areathat is actually projected is represented as a projection area 163 a,and the other area 163 b is represented as a non-projection area. Inthis case, the image processing/controlling unit 90 designates thecut-out area 170 that is larger than the area of the image datacorresponding to the image of the projection area 163 a by at least thenumber of lines corresponding to a change of a case where the projectionangle θ according to the projection lens 12 maximally changes during aperiod of two vertical synchronization signals VD for the memory T₁.

The image processing/controlling unit 90 reads the image data from thiscut-out area 170 at the timing of a next vertical synchronization signalVD after the vertical synchronization signal VD for writing the imagedata D₁ into the memory T₁. In this way, at the timing of the projectionangle θ₃, the image data to be projected is read from the memory T₁, issupplied to the display element 114 with necessary image processingbeing performed therefor in a later stage, and is projected from theprojection lens 12.

At the timing of the next vertical synchronization signal VD after thevertical synchronization signal VD for which the image data D₁ is input,the image data D₂ is input to the image processing/controlling unit 90.At this timing, the image data D₁ is written into the memory Y₁.Accordingly, the image processing/controlling unit 90 writes the imagedata D₂ into the memory Y₂ (timing WD₂ illustrated in Chart 215). Thesequence of writing the image data D₂ into the memory Y₂ at this time issimilar to the sequence of writing the image data D₁ described aboveinto the memory Y₁, and the sequence for the image is similar to thatdescribed above (see FIG. 12B).

In other words, the image processing/controlling unit 90 sequentiallyreads the image data D₂ in the vertical direction over the lines foreach pixel up to the pixel positioned at the upper end of the image witha pixel positioned on the lower left corner of the image being set as areading start pixel, and next, pixels are read in the vertical directionwith a pixel positioned on the right side neighboring to the pixelpositioned at the reading start position of the vertical direction beingset as a reading start pixel (timing RD₂ illustrated in Chart 215). Thisoperation is repeated until the reading of a pixel positioned on theupper right corner of the image is completed. The imageprocessing/controlling unit 90 sequentially writes (timing WD₂represented in Chart 216) the pixel of the image data D₂ read from thememory Y₂ in this way into the memory T₂ toward the line direction foreach pixel (see the left side in FIG. 13A).

The image processing/controlling unit 90 designates an address of thedesignated cut-out area to the memory T₂ and reads image data of thearea designated as the cut-out area from the memory T₂ at timing RD₂represented in Chart 216. At this time, as described above, the imageprocessing/controlling unit 90 designates an area lager than the area ofthe image data corresponding to the projected image as the cut-out area170 in consideration of a change in the projection angle θ for thememory T₂.

The image processing/controlling unit 90 reads the image data from thiscut-out area 170 at the timing of a next vertical synchronization signalVD after the vertical synchronization signal VD for writing the imagedata D₂ into the memory T₂. In this way, the image data of the cut-outarea 170 of the image data D₂ input to the image processing/controllingunit 90 at the timing of the projection angle θ₂ is read from the memoryT₂ at the timing of the projection angle θ₄, is supplied to the displayelement 114 with necessary image processing being performed therefor ina later stage, and is projected from the projection lens 12.

Thereafter, similarly, for the image data D₃, D₄, D₅, . . . , theprocess is sequentially performed using a set of the memories Y₁ and T₁and a set of the memories Y₂ and T₂ in an alternate manner.

As described above, according to each embodiment, in the image memory101, an area of the memories Y₁ and Y₂ used for writing and readingimage data with the size of horizontal 1920 pixels×vertical 1080 pixels(lines) and an area of the memories T₁ and T₂ used for writing andreading image data with the size of horizontal 1080 pixels×vertical 1920pixels (lines) are arranged. The reason for this is that, generally,DRAM (Dynamic Random Access Memory) used in an image memory has anaccess speed for the vertical direction that is lower than an accessspeed for the horizontal direction. In a case where another memory,which is easily randomly accessible, having access speeds of the samelevel for the horizontal direction and the vertical direction is used, aconfiguration may be employed in which a memory having a capacitycorresponding to the image data is used in both the cases.

Geometric Distortion Correction

Next, the geometric distortion correction for the image data that isperformed by the projector device 1 according to this embodiment will bedescribed.

FIGS. 14 and 15 are diagrams that illustrate the relation between theprojection direction of the projection lens 12 of the projector device 1for a screen 1401 and the projection image projected onto the screen1401 that is the projection face. As illustrated in FIG. 14, in a casewhere the projection angle is 0°, and the optical axis of the projectionlens 12 is perpendicular to the screen 1401, a projection image 1402 hasa rectangular shape that is the same as the image data projected fromthe projector device 1, and a distortion does not occur in theprojection image 1402.

However, as illustrated in FIG. 15, in a case where the image data isprojected in an inclined state with respect to the screen 1401, theprojection image 1502 to be a rectangular shape is distorted to be in atrapezoidal shape, in other words, a so-called trapezoidal distortionoccurs.

For this reason, conventionally, by performing a geometric distortioncorrection such as a trapezoidal distortion correction (keystonecorrection) transforming image data to be projected into a trapezoidalshape in a direction opposite to a trapezoidal shape generated in aprojection image on a projection face such as a screen, as illustratedin FIGS. 16A and 16B, a projection image having a rectangular shapewithout any distortion on the projection face is displayed on theprojection face. FIG. 16A illustrates an example of a projection imagebefore a geometric distortion correction is performed for the image dataof the projection image.

FIG. 16B illustrates an example of a projection image after a geometricdistortion correction is performed for the image data of the projectionimage illustrated in FIG. 16A. In the conventional trapezoidaldistortion correction, in order not to perform display of a peripheralarea 1602 of a corrected projection image 1601, in other words, displayof the area 1602 of a difference between an area 1603 of the projectionimage of a case where a correction is not performed and the area of theprojection image 1601 after the correction, image data corresponding toblack is input to the display device, or the display device iscontrolled so as not to be driven.

The method of designating a cut-out area using Equations (3) and (4)described above is based on a cylindrical model in which the projectionface 130, for which projection is performed by the projection lens 12,is assumed to be a cylinder having the rotation shaft 36 of the drumunit 10 as its center. However, actually, the projection face 130 isfrequently considered to be a perpendicular face (hereinafter, simplyreferred to as a “perpendicular face”) forming an angle of 90° withrespect to the projection angle θ=0°. In a case where image data of thesame number of lines is cut out from the image data 140 and is projectedto the perpendicular face, as the projection angle θ increases, an imageprojected to the perpendicular face grows in the vertical direction.Thus, after the process of the cutting-out unit, the image processorperforms image processing as below.

An image that is projected onto a perpendicular face will be describedwith reference to FIGS. 17 and 18. As illustrated in FIG. 17, a casewill be considered in which an image is projected from the projectionlens 12 onto a projection face 204 that is disposed to be separate froma position 201 by a distance r with the position 201 being the positionof the rotation shaft 36 of the drum unit 10.

In the cylindrical model described above, a projection image isprojected with an arc 202 that has the position 201 as its center andhas a radius r being the projection face. Each point on the arc 202 hasthe same distance from the position 201, and the center of the luminousfluxes of light projected from the projection lens 12 is a radius of acircle including the arc 202. Accordingly, even when the projectionangle θ is increased from an angle θ₀ of 0° to an angle θ₁, an angle θ₂,. . . , the projection image is projected to the projection face withthe same size all the time.

On the other hand, in a case where an image is projected from theprojection lens 12 onto the projection face 204 that is a perpendicularface, when the projection angle θ is increased from an angle θ₀ to anangle θ₁, an angle θ₂, . . . , a position on the projection face 204 towhich the center of luminous fluxes of light emitted from the projectionlens 12 is projected changes according to the characteristics of atangent function as a function of the angle θ. Accordingly, theprojection image grows to the upper side according to a ratio Mrepresented in the following Equation (9) as the projection angle θincreases.

M=(180×tan θ)/(θ×π)  (9)

According to Equation (9), for example, in the case of the projectionangle θ=45°, the projection image grows at the ratio of about 1.27times. In addition, in a case where the projection face W is much higherthan the length of the radius r, and projection at the projection angleθ=60° can be performed, in the case of the projection angle θ=60°, theprojection image grows at the ratio of about 1.65 times.

In addition, as illustrated in FIG. 18 as an example, a line gap 205 inthe projection image on the projection face 204 is widened as theprojection angle θ increases. In this case, the line gap 205 is widenedbased on Equation (9) described above in accordance with the position onthe projection face 204 within one projection image.

Thus, projector device 1 performs a reduction process at the ratio ofthe reciprocal of Equation (9) described above according to theprojection angle θ of the projection lens 12 for the image data of animage to be projected. In this reduction process, image data ispreferably larger than the image data cut out based on the cylindricalmodel. In other words, while the image data depends on the height of theprojection face 204 that is a perpendicular face, in the case of theprojection angle θ=45°, the projection image grows at the ratio of about1.27 times, and accordingly, the image data is reduced at the ratio ofthe reciprocal thereof that is about 78%.

As an example, when image data input to the projector device 1 is storedin the image memory 101, the image processing/controlling unit 90, forthe image data, by using the ratio of the reciprocal of Equation (9)described above, performs a reduction process for the image data inadvance for each line of an image at the time of projecting the imagedata. In the reduction process, a low pass filter process is performedfor lines (pixels in the vertical direction) with a reduction ratedepending on the projection angle θ by using a low pass filter ofseveral taps, thereby thinning out the lines. More precisely, in the lowpass filter process, it is preferable that a limit value of the band ofthe low pass filter is also changed depending on the projection angle θ.However, the reduction process is not limited thereto, but generallinear interpolation may be used in which the characteristic of thefilter is determined to be uniform with a reduction rate correspondingto a maximum projection angle θ, or the characteristic of the filter isdetermined to be uniform with a reduction rate corresponding to almost ½of the maximum projection angle θ. In addition, after the filterprocess, for the lines to be thinned out, it is preferable thatsub-sampling is performed depending on the projection angle θ within thescreen.

The process is not limited thereto. Thus, a process of uniformlyperforming a thinning-out process with a reduction rate corresponding toa maximum projection angle θ, uniformly performing a thinning-outprocess with a reduction rate corresponding to almost ½ of the maximumprojection angle θ, or the like may be performed. In a case where thelow pass filter process and the thinning-out process are to be performedmore precisely, by dividing image data into several areas in thedirection of the lines and uniformly performing the process for eachdivided area, a more improved characteristic can be acquired.

In addition, in each embodiment, while the image processing using thisEquation (9) is performed when the image processing/controlling unit 90stores image data in the image memory 101, the present invention is notlimited thereto. For example, the image processing using Equation (9)may be configured to be performed for the image data read from the imagememory 101.

Furthermore, in an environment in which the projector device 1 isactually used, there is a limit on the height of the projection face204, and it is considered that there are many cases where the face 203is formed at a position 200 of a certain height to be repeatedly turnedby 90°. This face 203 can be used as the projection face of theprojector device 1. In such a case, an image projected onto theprojection face 203 is reduced with a characteristic opposite to that ofthe image projected onto the projection face 204 described above as theprojection angle θ further increases, and the projection position passesthrough the position 200 and faces toward a right above side (projectionangle θ=90°).

For this reason, in a case where an image according to the image data isprojected at projection angles 0° and 90°, the reduction process usingEquation (9) is not performed for the image data to be projected. Inaddition, in a case where the length (height) of the projection face 204and the length of the projection face 203 are almost the same, thereduction process using Equation (9) for the image data to be projectedis performed as a symmetrical process of a reduction process from theprojection angle 0° to the position 200 of the uppermost portion of theprojection face W and a reduction process from the position 200 to theprojection angle 90°. Accordingly, a load for the reduction processperformed by the image processing/controlling unit 90 can be decreased.

In the example described above, the description has been presented witha perpendicular face forming an angle of 90° with respect to theprojection angle θ=0° being assumed. Depending on the rotation angle ofthe drum unit 10, a case may be considered in which projection isperformed for a flat face forming an angle of 180° with respect to theprojection angle θ=0°. In a case where image data of the same lines iscut out from the image data 140 and is projected onto the face, aprojected image is reduced in the vertical direction as the projectionangle θ increases. Thus, for the image data read from the image memory101, image processing that is opposite to that described above isperformed.

In other words, as the projection angle θ is increased from the angle θ₀to the angle θ₁, and the angle θ₂, a distance from the projection unitto the projection face is changed to decrease. Thus, opposite to thedescription presented above, the projector device 1 performs anenlargement process for the image data of an image to be projectedaccording to the projection angle θ of the projection lens 12.

As above, in a case where the distance from the projection lens 12 tothe projection face decreases as the projection direction is changedfrom the first projection direction to the second projection direction,the image cutting-out unit of the projector device 1 may perform anenlargement process based on the projection angle θ for each pixel ofthe cut-out image data.

First Embodiment

Next, a first embodiment will be described. FIG. 19 is a block diagramthat illustrates an example of the functional configuration of aprojector device 1 a according to the first embodiment. In FIG. 19, thesame reference numeral is assigned to each portion common to thatillustrated in FIG. 4 described above, and detailed description thereofwill not be presented.

The external appearance and the structure of the projector device 1 aaccording to the first embodiment are similar to those of the projectordevice 1 described with reference to FIGS. 1A, 1B, 2A, and 2B.

In the case illustrated in FIG. 19, the image processing/controllingunit 90 illustrated in FIG. 4 includes: a geometric distortioncorrection unit 100; an image memory 101; an image control unit 103; andan extended function control unit 109. In addition, an input controlunit 119 receives a user's operation input from an operation unit 14 asan event. The input control unit 119, for example, forms a part of thefunction of the overall control unit 120.

The image control unit 103 receives image data as an input and storesthe image data with designated output resolution in the image memory101. The image control unit 103, as illustrated in FIG. 19, includes anoutput resolution control unit 1031 and a memory controller 1032.

The output resolution control unit 1031 receives resolution from thegeometric distortion correction unit 100 through the extended functioncontrol unit 109 and outputs the received resolution to the memorycontroller 1032 as output resolution.

The memory controller 1032 receives image data 1035 of 1920 pixels×1080pixels of a still image or a moving image as an input and stores theinput image data 1035 of 1920 pixels×1080 pixels in the image memory 101with the output resolution input from the output resolution control unit1031.

In addition, an image shaping unit, which shapes the input image data1035 input with an arbitrary size into image data of the size of 1920pixels×1080 pixels, may be disposed on the former stage of the memorycontroller 1032.

The geometric distortion correction unit 100 calculates a firstcorrection coefficient relating to a trapezoidal distortion correctionof the horizontal direction (first direction) of a geometric distortionand a second correction coefficient relating to a geometric distortioncorrection according to slow extension in the vertical direction (seconddirection), acquires a cut-out range, cuts out an image of an area ofthe cut-out range from image data stored in the image memory 101,performs a geometric distortion correction and image processingtherefor, and outputs the processed image to the display element 114. Indescription presented below, in a case where the first correctioncoefficient and the second correction coefficient are not discriminatedfrom each other or do not need to be discriminated from each other, thefirst correction coefficient and the second correction coefficient willbe simply referred to as correction coefficients.

The geometric distortion correction unit 100, as illustrated in FIG. 19,includes: a correction control unit 108; a memory controller 107; and animage processor 102. In addition, a zoom instruction and a view angle1042 derived based on a zoom magnification relating to the zoominstruction are supplied from the view angle control unit 106 to thegeometric distortion correction unit 100.

The correction control unit 108 receives a projection angle 1041 fromthe rotation control unit 104 as an input and receives a view angle 1042from the view angle control unit 106 as an input. Then, the correctioncontrol unit 108, based on the projection angle 1041 and the view angle1042 that have been input, calculates the first correction coefficientand the second correction coefficient used for eliminating a geometricdistortion occurring in a projected image according to the projectiondirection, and outputs the first correction coefficient and the secondcorrection coefficient to the memory controller 107.

In addition, the correction control unit 108, based on the projectionangle 1041, the view angle 1042, the first correction coefficient, andthe second correction coefficient, determines a cut-out range of theimage data 1035 such that the size of image data after the geometricdistortion correction includes a displayable size of the display element114 and outputs the determined cut-out range to the memory controller107 and the extended function control unit 109. At this time, thecorrection control unit 108 designates a cut-out area of the image databased on the angle of the projection direction of the projection lens12.

The memory controller 107 cuts out (extracts) an image area of thecut-out range determined by the correction control unit 108 from all thearea of a frame image relating to image data stored in the image memory101 and outputs the image area as image data.

In addition, the memory controller 107 performs a geometric distortioncorrection for the image data cut out from the image memory 101 by usingthe first correction coefficient and the second correction coefficientand outputs image data after the geometric distortion correction to theimage processor 102. Here, the first correction coefficient, the secondcorrection coefficient, and the geometric distortion correction will bedescribed later in detail.

The image data output from the memory controller 107 is supplied to theimage processor 102. The image processor 102, for example, by using amemory not illustrated in the figure, performs image processing for thesupplied image data and outputs the processed image data to the displayelement 114 as image data 1036 of 1280 pixels×720 pixels. For example,the image processor 102 performs a size converting process for the imagedata supplied from the memory controller 107 such that the sizecoincides with the size of the display element 114.

In addition to that, the image processor 102 may perform various kindsof image processing such as the size conversion process executed througha general linear transformation process, which is described in the imageprocessing/controlling unit 90 illustrated in FIG. 4, an interpolationprocess, a thinning out process, an edge enhancement process, a low passfilter process, and a halftone mixing process.

The image data 1036 output from the image processor 102 is supplied tothe display element 114. Actually, this image data is supplied to thedrive circuit that drives the display element 114. The drive circuitdrives the display element 114 based on the supplied image data.

The extended function control unit 109 receives a cut-out range from thecorrection control unit 108 as an input and outputs resolution includingthe cut-out range to the output resolution control unit 1031 as outputresolution.

However, as already described with reference to FIG. 16B, in theconventional trapezoidal correction (keystone correction) process, inorder not to perform display for the peripheral area 1602 of thecorrected projection image 1601, in other words, the area 1602 of adifference between the area 1603 of a projected image of a case whereany correction is not performed and the area of a projection image 1601after a correction, image data corresponding to black is controlled tobe input to the display device, or the display device is controlled notto be driven. Accordingly, the pixel area of the display device is noteffectively used, and a decrease in the brightness of the actualprojection area is caused.

Recently, in accordance with wide use of high-resolution digital camerasand the like, the resolution of video content is improved, and there arecases where the resolution of the video content is higher than theresolution of the display device. For example, in a projector devicesupporting up to the full HD of 1920 pixels×1080 pixels as an inputimage for a display device having resolution of 1280 pixels×720 pixels,the input image is scaled in a former stage of the display device, andaccordingly, the resolution is matched for enabling the whole inputimage to be displayed on the display device.

On the other hand, instead of performing such a scaling process, asillustrated in FIGS. 20A and 20B, an image of a partial area of inputimage data may be cut out and displayed on the display device. Forexample, from input image data having 1920 pixels×1080 pixelsillustrated in FIG. 20A, as illustrated in FIG. 20B, an image of an areaof 1280 pixels×720 pixels corresponding to the resolution of an outputdevice is cut out and is displayed on the display device. Even in such acase, when the projection lens is inclined, as illustrated in FIG. 21A,a trapezoidal distortion occurs in the projection image. Thus, when thetrapezoidal distortion correction (keystone correction) is performed, asillustrated in FIG. 21B, in order not to perform display of adifferential area between the area of the projection image of a casewhere any correction is not performed and the area of the projectionimage after the correction, image data corresponding to black is inputto the display device, or the display device is controlled so as not tobe driven. Accordingly, a state is formed in which the pixel area of thedisplay device is not effectively used. However, in such a case, asillustrated in FIGS. 20A and 20B, the projection image that is output isa part of the input image data.

For this reason, according to the projector device 1 a according to thisfirst embodiment, as illustrated in FIG. 22, an image of the unused arearemaining after being originally cut out from the input image data isused for the peripheral area 1602 of the image data after the correctiondescribed above, and, for example, as illustrated in FIG. 23, all theinput image data is cut out, and the projection image is displayed suchthat the center of the projection image in the vertical directioncoincides with that of the projection image for which the geometricdistortion correction has not been performed, and the amount ofinformation lacking in the peripheral area 1602 is supplemented. In thisway, according to this first embodiment, by effectively utilizing theimage of the unused area, the effective use of the displayable area isrealized. By comparing FIG. 23 with FIG. 21B, it can be understood thatthe area of the peripheral area is decreased in FIG. 23, and moreinformation can be represented (effectively used). Hereinafter, detailsof such a geometric distortion correction, first, the calculation ofcorrection coefficients used for performing the geometric distortioncorrection and next, a method of supplementing the amount of informationwill be described.

The correction control unit 108 of the geometric distortion correctionunit 100, as described above, calculates a first correction coefficientand a second correction coefficient based on the projection angle 1041and the view angle 1042. Here, the first correction coefficient is acorrection coefficient for performing a correction of the image data inthe horizontal direction, and the second correction coefficient is acorrection coefficient for performing a correction of the image data inthe vertical direction. The correction control unit 108 may beconfigured to calculate the second correction coefficient for each lineconfiguring the image data (cut-out image data) of the cut-out range.

In addition, the correction control unit 108, for each line from theupper side to the lower side of the image data of the cut-out range,calculates a linear reduction rate for each line based on the firstcorrection coefficient.

The relation between the projection angle 1041 and the correctioncoefficient and the correction coefficient and a correction amount for atrapezoidal distortion calculated based on the projection angle 1041will be described in detail. FIG. 24 is a diagram that illustrates majorprojection directions and projection angles θ of the projection faceaccording to the first embodiment.

Here, the projection angle θ is an inclination angle of the optical axisof projection light emitted from the projection lens 12 with respect tothe horizontal direction. Hereinafter, an inclination angle of a casewhere the optical axis of the projection light is in the horizontaldirection is set as 0°, a case where the drum unit 10 including theprojection lens 12 is rotated to the upper side, in other words, theelevation angle side will be defined as positive, and a case where thedrum unit 10 is rotated to the lower side, in other words, thedepression angle side will be defined as negative. In such a case, ahoused state in which the optical axis of the projection lens 12 faces afloor face 222 disposed right below corresponds to a projection angle of−90°, and a horizontal state in which the projection direction faces thefront side of a wall face 220 corresponds to a projection angle of 0°,and a state in which the projection direction faces a ceiling 221disposed right above corresponds to a projection angle of +90°.

A projection direction 231 is a direction of a boundary between the wallface 220 and the ceiling 221 that are two projection faces adjacent toeach other. A projection direction 232 is, the projection direction ofthe projection lens 12 in a case where an upper face, which correspondsto a first side, of one pair of sides disposed in a directionperpendicular to the vertical direction that is the moving direction ofa projection image approximately coincides with the boundary in theprojection image on the wall face 220.

A projection direction 233 is the projection direction of the projectionlens 12 in a case where a lower side, which corresponds to a secondside, of the above-described one pair of sides of the projection imageof the ceiling 221 approximately coincides with the boundary. Aprojection direction 234 is the direction of the ceiling 221 right abovethe projector device 1 a and corresponds to a state in which the opticalaxis of the projection lens 12 and the ceiling 221 cross each other atright angles. The projection angle at this time is 90°.

In the example illustrated in FIG. 24, the projection angle θ in thecase of the projection direction 230 is 0°, the projection angle in thecase of the projection direction 232 is 35°, the projection angle θ inthe case of the projection direction 231 is 42°, and the projectionangle θ in the case of the projection direction 233 is 49°.

A projection direction 235 is a direction in which projection is startedby the projector device 1 a that is acquired by rotating the projectionlens from a state in which the projection lens is positioned toward theright below side (−90°), and the projection angle θ at this time is−45°. A projection direction 236 is the projection direction of theprojection lens in a case where an upper face, which corresponds to afirst side, of one pair of sides disposed in a direction perpendicularto the moving direction of a projection image approximately coincideswith a boundary between the floor face 222 and the wall face 220 in theprojection image on the floor face 222. The projection angle θ at thistime will be referred to as a second boundary start angle, and thesecond boundary start angle is −19°.

A projection direction 237 is a direction of a boundary between thefloor face 222 and the wall face 220 that are two projection facesadjacent to each other. The projection angle θ at this time will bereferred to as a second boundary angle, and the second boundary angle is−12°.

A projection direction 238 is the projection direction of the projectionlens in a case where a lower face, which corresponds to a second face,of the above-described one pair of sides of the projection image on thewall face 220 approximately coincides with a boundary between the floorface 222 and the wall face 220. The projection angle θ at this time willbe referred to as a second boundary end angle, and the second boundaryend angle is −4°.

Hereinafter, an example of the geometric distortion correction (thetrapezoidal distortion correction will be used as an example) will bedescribed. FIG. 25 is a graph that illustrates a relation between theprojection angle and the first correction coefficient according to thefirst embodiment. In FIG. 25, the horizontal axis represents theprojection angle θ, and the vertical axis represents the firstcorrection coefficient.

The first correction coefficient takes a positive value or a negativevalue. In a case where the first correction coefficient is positive, itrepresents a correction direction for compressing the length of theupper side of the trapezoid of the image data. On the other hand, in acase where the first correction coefficient is negative, it represents acorrection direction for compressing the length of the lower side of thetrapezoid of the image data. In addition, as described above, in a casewhere the first correction coefficient is “1” or “−1”, the correctionamount for the trapezoidal distortion is zero, whereby the trapezoidaldistortion correction is completely cancelled.

In FIG. 25, the projection directions 235, 236, 237, 238, 230, 232, 231,233, and 234 illustrated in FIG. 24 are illustrated in association withprojection angles thereof. As illustrated in FIG. 25, in a range 260from a projection angle of −45° for the projection direction 235 to aprojection angle of −12° for the projection direction 237, theprojection lens projects the floor face 222.

In addition, as illustrated in FIG. 25, in a range 261 from a projectionangle of −12° for the projection direction 237 to a projection angle of0° for the projection direction 230, the projection lens projects thewall face 220 downward. Furthermore, as illustrated in FIG. 25, in arange 262 from a projection angle of 0° for the projection direction 230to a projection angle of 42° for the projection direction 231, theprojection lens projects the wall face 220 upward.

In addition, as illustrated in FIG. 25, in a range 263 from a projectionangle of 42° for the projection direction 231 to a projection angle of90° for the projection direction 234, the projection lens projects theceiling 221.

The correction control unit 108 calculates a trapezoidal distortioncorrection amount based on a first correction coefficient according toeach projection angle θ denoted by a solid line in FIG. 25 and performsa trapezoidal distortion correction for the image data based on thecalculated correction amount. In other words, the correction controlunit 108 calculates a first correction coefficient corresponding to theprojection angle output from the rotation control unit 104. In addition,the correction control unit 108, based on the projection angle,determines whether the projection direction of the projection lens 12 isthe projection direction that is an upward projection direction withrespect to the wall face, the projection direction toward the face ofthe ceiling, the projection direction that is a downward direction withrespect to the wall face, or the projection direction toward the floorface and derives a correction direction of the trapezoidal distortioncorrection for the image data in accordance with the projectiondirection.

The correction control unit 108 calculates a trapezoidal distortioncorrection amount based on a correction coefficient according to eachprojection angle θ denoted by a solid line in FIG. 25 and performs atrapezoidal distortion correction for the image data based on thecalculated correction amount. In other words, the correction controlunit 108 calculates a first correction coefficient corresponding to theprojection angle 1041 output from the rotation control unit 104. Inaddition, the correction control unit 108, based on the projection angleθ, determines whether the projection direction of the projection lens 12is the projection direction that is an upward projection direction withrespect to the wall face 220, the projection direction toward the faceof the ceiling 221, the projection direction that is a downwarddirection for the wall face 220, or the projection direction toward thefloor face 222 and derives a correction direction of the trapezoidaldistortion correction for the image data in accordance with theprojection direction.

Here, as illustrated in FIG. 25, between a projection angle of −45° atthe time of the projection direction 235 and the second boundary startangle (−19°) that is the projection angle θ at the time of theprojection direction 236 and between a projection angle of 0° at thetime of the projection direction 230 and the first boundary start angle(35°) that is the projection angle at the time of the projectiondirection 232, the correction coefficient is positive and graduallydecreases, and the correction amount for the trapezoidal distortiongradually increases. Here, the previous correction coefficient or theprevious correction amount is used for maintaining the shape of theprojection image projected onto the projection face to be a rectangle.

On the other hand, as illustrated in FIG. 25, between the secondboundary start angle (−19°) that is the projection angle θ at the timeof the projection direction 236 and the second boundary angle (−12°)that is the projection angle θ at the time of the projection direction237 and between the first boundary start angle (35°) that is theprojection angle θ of the projection direction 232 and the firstboundary angle (42°) that is the projection angle θ at the time of theprojection direction 231, the correction coefficient is positive andgradually increases so as to decrease a difference from “1” and is in adirection (a direction for cancelling the trapezoidal distortioncorrection) for weakening the degree of the trapezoidal distortioncorrection. In the projector device 1 a according to this firstembodiment, as described above, the correction coefficient is positiveand gradually increases, and the correction amount for the trapezoidaldistortion gradually decreases. Here, this increase may not be a graduallinear increase but may be an exponential increase or a geometricincrease as long as the increase is a continuous gradual increase.

In addition, as illustrated in FIG. 25, between the second boundaryangle (−12°) that is the projection angle θ at the time of theprojection direction 237 and the second boundary end angle (−4°) that isthe projection angle θ at the time of the projection direction 238 andbetween the first boundary angle (42°) that is the projection angle θ ofthe projection direction 231 and the first boundary end angle (49°) thatis the projection angle θ at the time of the projection direction 233,the correction coefficient is negative and gradually increases, and thecorrection amount for the trapezoidal distortion gradually increases. Inthe projector device 1 a according to this first embodiment, asdescribed above, the correction coefficient is negative and graduallyincreases, and the correction amount for the trapezoidal distortiongradually increases. Here, this increase may not be a gradual linearincrease but may be an exponential increase or a geometric increase aslong as the increase is a continuous gradual increase.

Here, as illustrated in FIG. 25, between the second boundary end angle(−4°) that is the projection angle θ at the time of the projectiondirection 238 and a projection angle of 0° at the time of the projectiondirection 230 and between the first boundary end angle (49°) that is theprojection angle θ at the time of the projection direction 233 and aprojection angle of 90° at the time of the projection direction 234, thecorrection coefficient is negative and gradually decreases, and thecorrection amount for the trapezoidal distortion gradually decreases.Here, the previous correction coefficient or the previous correctionamount is used for maintaining the shape of the projection imageprojected onto the projection face to be a rectangle.

Here, a technique for calculating the correction coefficient will bedescribed. In description presented below, a case will be described asan example in which the projector device 1 a shifts the projectiondirection from a state directly opposing the projection face of aprojection medium to the vertically upward direction. In addition, acorrection coefficient of a case where the projector device 1 a shiftsthe projection direction from the state of directly opposing theprojection face of a projection medium in the horizontal direction canbe similarly calculated.

FIG. 26 is a diagram that illustrates the calculation of the firstcorrection coefficient. In FIG. 26, a projection distance until lightemitted from the upper end (or the right end) of the display element 114of the projector device 1 a arrives at the projection face 250 isdenoted by a₁, and a projection distance until light emitted from thelower end (or the right end) of the display element 114 arrives at theprojection face 250 is denoted by a₂. In the case illustrated in FIG.26, the projection distance a₁ is a longest distance, and the projectiondistance a₂ is a shortest distance. In addition, in the case illustratedin FIG. 26, a ½ angle of the view angle α is an angle β. Furthermore,the length of the base of an isosceles triangle that has the view angleα as its apex angle and has a hypotenuse of a length a₁ is denoted byb₁, and the length of the base of an isosceles triangle that has thesame apex angle of 2β and has the hypotenuse having a length a₂ isdenoted by b₂. Furthermore, the vertical coordinate d_(y) (or thehorizontal coordinate d_(x)) of the lower end (or the right end) of thedisplay element 114 is denoted as zero, and the vertical coordinate (orthe horizontal coordinate) of the upper end (or the left end) is denotedby Y_SIZE (or X_SIZE). In addition, an arrow 251 represents the verticaldirection.

The first correction coefficient is the reciprocal (or the reciprocal ofa ratio between the left side and the right side) of a ratio between theupper side and the lower side of the projection image that is projectedto a projection medium so as to be displayed thereon and is the same asb₂/b₁ illustrated in FIG. 26. Accordingly, in the trapezoidal distortioncorrection, the upper side or the lower side (or the left side or theright side) of the image data is reduced by b₂/b₁ times.

Here, as illustrated in FIG. 26, b₂/b₁ is represented in the followingEquation (10) by using the projection distances a₁ and a₂.

$\begin{matrix}{\frac{b_{2}}{b_{1}} = \frac{a_{2}}{a_{1}}} & (10)\end{matrix}$

In the case illustrated in FIG. 26, when θ represents the projectionangle, and n represents a shortest distance from the projector device 1a to the projection face 250, the following Equation (11) is satisfied.Here, 0° 0<90°. A straight line representing the shortest projectiondistance n from the projector device 1 a to the projection face 250 is aperpendicular line with respect to the projection face 250.

n=a ₁ cos(θ+β)=a ₂ cos(θ−β)  (11)

By transforming Equation (11), the first correction coefficient can beacquired in the following Equation (12).

$\begin{matrix}{\frac{a_{2}}{a_{1}} = {\frac{\cos ( {\theta + \beta} )}{\cos ( {\theta - \beta} )} = {k( {\theta,\beta} )}}} & (12)\end{matrix}$

As above, the first correction coefficient is determined based on theangle β that is ½ of the view angle α and the projection angle θ. Basedon this Equation (12), in a case where the projection angle θ is 0°, inother words, in a case where the projection image is projected in adirection perpendicular to the projection face 250, the first correctioncoefficient is “1”, and the trapezoidal distortion correction amount iszero.

In addition, based on Equation (12), the first correction coefficientdecreases as the projection angle θ increases. The trapezoidaldistortion correction amount increases according to the value of thefirst correction coefficient, and accordingly, the trapezoidaldistortion of the projection image that becomes remarkable according toan increase in the projection angle θ can be appropriately corrected.

Furthermore, in a case where the projection image is projected to theceiling, the correction direction of the trapezoidal distortioncorrection changes, and accordingly, the correction coefficient isa₁/a₂. In addition, as described above, the sign of the first correctioncoefficient is negative.

In this embodiment, the correction control unit 108 calculates the firstcorrection coefficient based on Equation (12) when the projection angleθ is between the projection angle of −45° at the time of the projectiondirection 235 and the second boundary start angle (−19°) that is theprojection angle at the time of the projection direction 236, betweenthe projection angle of 0° at the time of the projection direction 230and the first boundary start angle (35°) that is the projection angle atthe time of the projection direction 232, between the second boundaryend angle (−4°) that is the projection angle at the time of theprojection direction 238 and the projection angle of 0° at the time ofthe projection direction 230, or between the first boundary end angle(49°) that is the projection angle of the projection direction 233 andthe projection angle of 90° at the time of the projection direction 234,described above.

On the other hand, the correction control unit 108 calculates the firstcorrection coefficient in a direction for lowering the degree of thecorrection without using Equation (12) when the projection angle isbetween the second boundary start angle (−19°) that is the projectionangle at the time of the projection direction 236 and the secondboundary angle (−12°) that is the projection angle at the time of theprojection direction 237 or between the first boundary start angle (35°)that is the projection angle at the time of the projection direction 232and the first boundary angle (42°) that is the projection angle at thetime of the projection direction 231.

In addition, the correction control unit 108 calculates the firstcorrection coefficient in a direction for raising the degree of thecorrection without using Equation (12) when the projection angle θ isbetween the second boundary angle (−12°) that is the projection angle atthe time of the projection direction 237 and the second boundary endangle (−4°) that is the projection angle at the time of the projectiondirection 238 or between the first boundary angle (42°) that is theprojection angle at the time of the projection direction 231 and thefirst boundary end angle (49°) that is the projection angle at the timeof the projection direction 233.

The calculation of the first correction coefficient is not limited tothat described above, and the correction control unit 108 may beconfigured to calculate the first correction coefficient using Equation(12) for all the projection angles θ.

In addition, the correction control unit 108, as represented in thefollowing Equation (13), multiplies the length H_(act) of the line ofthe upper side of the image data by a first correction coefficient k(θ,β) represented in Equation (12), thereby calculating the lengthH_(act)(θ) of the line of the upper side after the correction.

H _(act)(θ)=k(θ,β)×H _(act)  (13)

The correction control unit 108, in addition to the length H_(act)(θ) ofthe upper side of the image data, calculates a reduction rate of thelength of each line in a range from the line of the upper side to theline of the lower side. FIG. 27 is a diagram that illustrates thecalculation of lengths of lines from the upper side to the lower side.

As illustrated in FIG. 27, the correction control unit 108 calculatesthe length h_(act)(d_(y)) of each line from the upper side to the lowerside of the image data so as to be linear by using the followingEquation (14). Here, Y_SIZE represents the height of the image data, inother words, the number of lines. Thus, Equation (14) is an equation forcalculating the length h_(act)(d_(y)) of the line at a position of d_(y)from the lower side.

$\begin{matrix}\begin{matrix}{{h_{act}( d_{y} )} = {{K_{H}( d_{y} )} \times H_{act}}} \\{= {\{ {1 - {( {1 - \frac{\cos ( {\theta + \beta} )}{\cos ( {\theta - \beta} )}} ) \times \frac{d_{y}}{Y\_ SIZE}}} \} \times H_{act}}}\end{matrix} & (14)\end{matrix}$

In Equation (14), a part represented inside braces { } represents areduction rate for each line. Thus, the reduction rate k_(H)(d_(y)) isrepresented as in the following Equation (15). As above, the reductionrate can be acquired based on the projection angle θ and the view angleα (=2β).

$\begin{matrix}{{k_{H}( d_{y} )} = {1 - {( {1 - \frac{\cos ( {\theta + \beta} )}{\cos ( {\theta - \beta} )}} ) \times \frac{d_{y}}{Y\_ SIZE}}}} & (15)\end{matrix}$

Another method of calculating the first correction coefficient will nowbe described. The first correction coefficient may be calculated from aratio between the length of the side of the projection image at theprojection angle 0° and the length of the side of the projection imageat the projection angle θ. In such a case, the length h_(act)(d_(y)) ofeach line from the upper side to the lower side of the image data can berepresented as in the following Equation (16).

$\begin{matrix}{{h_{act}( d_{y} )} = {{\cos ( {( {\theta + \beta} ) - {2\beta \times \frac{{Y\_ SIZE} - d_{y}}{Y\_ SIZE}}} )} \times H_{act}}} & (16)\end{matrix}$

Next, the calculation of a second correction coefficient will bedescribed. FIG. 28 is a diagram that illustrates the calculation of thesecond correction coefficient. The method of designating a cut-out areausing Equations (3) and (4) described above is based on a cylindricalmodel in which the projection face, for which projection is performed bythe projection lens 12, is assumed to be a cylinder having the rotationshaft 36 of the drum unit 10 as its center. However, actually, theprojection face is frequently considered to be a perpendicular face(hereinafter, simply referred to as a “perpendicular face”) forming anangle of 90° with respect to the projection angle θ=0°. In a case whereimage data of the same number of lines is cut out from the image data140 and is projected to the perpendicular face, as the projection angleθ increases, an image projected to the perpendicular face grows in thevertical direction. Thus, the correction control unit 108 calculates thesecond correction coefficient as below, and a geometric distortioncorrection for the image data is performed using the second correctioncoefficient by the memory controller 107.

A projection space illustrated in FIG. 28 is the same as the projectionspace illustrated in FIG. 26. In the calculation of the secondcorrection coefficient, first, by using the following Equation (17), thevertical coordinate d_(y) on the display element 114 is converted intoan angle d_(a) of which the value is zero at the center of the viewangle α. In such a case, the angle d_(a), as represented in thefollowing Equation (17), can take a value from −β to +β.

$\begin{matrix}{d_{\alpha} = {{{\frac{2\beta}{Y\_ SIZE} \times d_{y}} - \beta - {2\beta}} \leq d_{\alpha} \leq \beta}} & (17)\end{matrix}$

Here, a reduction coefficient k_(V)(d_(α)) of the vertical direction foreach vertical coordinate d_(y) can be acquired by using the followingEquation (18).

k _(V)(d _(a))=cos(θ)−sin(θ)tan(d _(a))  (18)

Thus, the second correction coefficient k_(V)(d_(y)) is acquired in thefollowing Equation (19) based on Equations (17) and (18) describedabove.

$\begin{matrix}{{k_{V}( d_{y} )} = {{\cos (\theta)} - {{\sin (\theta)}{\tan ( {{\frac{2\beta}{Y\_ SIZE} \times d_{y}} - \beta} )}}}} & (19)\end{matrix}$

In this way, the correction control unit 108 calculates the secondcorrection coefficient by using Equation (19) described above inaccordance with the projection angle θ of the projection lens 12 andmultiples image data read from the memory controller 107 by the secondcorrection coefficient according to the height (vertical coordinated_(y)) of the line, thereby performing a reduction process for the imagedata to be projected. Accordingly, a geometric distortion of theprojection image formed in the vertical direction is corrected.

In addition, the second correction coefficient may be used for eachvertical coordinate by using Equation (19) described above or may beacquired by performing linear interpolation based on the secondcorrection coefficient acquired by using Equation (19) described abovefor a specific vertical line.

FIG. 29 is a graph that illustrates the relation between the verticalcoordinate and the second correction coefficient. In addition, FIG. 29illustrates a case where Y_SIZE=800, the projection angle θ is set to60°, and the ½ view angle β is set to 28°. In FIG. 29, a characteristicline L₁ represents a value (a second correction coefficient: atheoretical value) acquired by using Equation (19), a characteristicline L₂ represents a second correction coefficient acquired byperforming linear interpolation based on values (second correctioncoefficients: theoretical values) of two points acquired by usingEquation (19) for the upper and lower ends (d_(y)=0 and d_(y)=Y_SIZE) ofthe image data, and a characteristic line L₃ represents a secondcorrection coefficient that is acquired by performing linearinterpolation of values (second correction coefficients: theoreticalvalues) acquired by using Equation (19) for the upper and lower ends ofthe image data and one or more vertical coordinates (in the caseillustrated in FIG. 29, three points of d_(y)=200, d_(y)=400, andd_(y)=600) positioned to be equally spaced therebetween. As above, byacquiring the second correction coefficient through the linearinterpolation and correcting the geometric distortion of the image forthe vertical direction, the processing load for the correction controlunit 108 can be decreased.

In addition, the correction control unit 108 acquires a cut-out range ofthe image data based on the first correction coefficient, the reductionrate, and the second correction coefficient calculated as describedabove and outputs the cut-out range to the extended function controlunit 109 and the memory controller 107.

For example, in a case where the view angle α is 10°, and the projectionangle θ is 30°, the projection image is distorted to be in a trapezoidalshape, and the length of the upper side of the trapezoid is about 1.28times of the length of the lower side. Accordingly, in order to correctthe horizontal-direction distortion, the correction control unit 108calculates the first correction coefficient as 1/1.28, reduces the firstline of the upper side of the image data at 1/1.28 times, and setsreduction rates of lines to be linear such that the final line is scaledto the original size. In other words, the number of pixels for the firstline of the output of the image data is reduced from 1280 pixels to 1000pixels (1280/1.28=1000), whereby the trapezoidal distortion iscorrected.

However, in this state, as described above, for the first line, imagedata of 280 pixels (1280−1000=280) is not projected, and the number ofeffective projection pixels decreases. Thus, in order to supplement theamount of information as illustrated in FIG. 23, the memory controller107, for the first line, reads a signal of 1.28 times of the horizontalresolution of the image data from the image memory 101, and thecorrection control unit 108 determines a cut-out range of the image dataso as to perform this process for each line.

The extended function control unit 109 achieves the role of associatingthe image control unit 103 with the geometric distortion correction unit100. In other words, in an area for which all the outputs of the imagedata is painted in black according to the geometric distortioncorrection in a conventional case, information of the image data isrepresented. For this reason, the extended function control unit 109, inaccordance with the cut-out range input from the correction control unit108, sets the output resolution to be higher than the resolution of 1280pixels×720 pixels at the time of outputting the image data in the outputresolution control unit 1031. In the example described above, since theenlargement/reduction rate is one, the extended function control unit109 sets the output resolution as 1920 pixels×1080 pixels.

In this way, the memory controller 1032 of the image control unit 103stores the input image data in the image memory 101 with the resolutionof 1920 pixels×1080 pixels. Accordingly, the image data in the cut-outrange can be cut out in the state as illustrated in FIG. 23 in which theamount of information is supplemented from the memory controller 107 ofthe geometric distortion correction unit 100.

In addition, the memory controller 107 performs the geometric distortioncorrection as below by using the first correction coefficient, thereduction rate, and the second correction coefficient calculated asdescribed above. In other words, the memory controller 107 multipliesthe upper side of the image data of the cut-out range by the firstcorrection coefficient and multiplies each line of the upper side to thelower side of the image data of the cut-out range by a reduction rate.In addition, the memory controller 107 generates lines corresponding toa display pixel number from the image data of the lines configuring theimage data of the cut-out range based on the second correctioncoefficient.

Next, an example of the cutting out of image data and the geometricdistortion correction performed by the geometric distortion correctionunit 100 according to this embodiment will be described with beingcompared with a conventional case. In FIG. 23 described above, anexample has been described in which all the input image data is cut out,and the projection image is displayed such that the center of theprojection image in the vertical direction coincides with the projectionimage for which the geometric distortion correction has not beenperformed. Hereinafter, with reference to FIGS. 30A to 30D, 31A to 31D,32A to 32D, and 33A to 33D, an example will be described in which theinput image data is cut out in accordance with the number of pixels ofthe display element 114, and the geometric distortion correction isperformed with the cut-out range also including the area of thegeometric distortion that may occur in the projection image inaccordance with the projection direction being set as the cut-out imagedata.

FIGS. 30A to 30D are diagrams that illustrate examples of cutting out ofimage data, image data on the display element 114, and the projectionimage in a case where the projection angle is 0°. In a case where theprojection angle is 0°, when image data 2700 of 1920 pixels×1080 pixelsis input (FIG. 30A), the memory controller 107 cuts outs a range of 1280pixels×720 pixels that is the resolution of the display element 114 fromthe image data (image data 2701 illustrated in FIG. 30B). For theconvenience of description, a center portion is assumed to be cut out(hereinafter, the same). Then, the memory controller 107 does notperform a geometric distortion correction (image data 2702 illustratedin FIG. 30C) but, as illustrated in FIG. 30D, projects the cut-out imagedata onto the projection face as a projection image 2703.

FIGS. 31A to 31D are diagrams that illustrate examples of cutting out ofimage data, image data on the display element 114, and a projectionimage in a case where the projection angle is greater than 0°, and ageometric distortion correction is not performed.

In a case where the projection angle is greater than 0°, when image data2800 of 1920 pixels×1080 pixels is input (FIG. 31A), a range of 1280pixels×720 pixels that is the resolution of the display element 114 iscut out from the image data (image data 2801 illustrated in FIG. 31B).Then, since the geometric distortion correction (trapezoidal distortioncorrection) is not performed (image data 2802 illustrated in FIG. 31C),as illustrated in FIG. 31D, a projection image 2803 in which atrapezoidal distortion has occurred is projected to the projection face.In other words, in the horizontal direction, the projection image isdistorted in a trapezoidal shape in accordance with the projectionangle, and, in the vertical direction, a distance of the projection faceis different in accordance with the projection angle, whereby a verticaldistortion in which the height of the line increases in the upwardvertical direction occurs.

FIGS. 32A to 32D are diagrams that illustrate examples of cutting out ofimage data, image data on a display element 114, and a projection imagein a case where the projection angle is greater than 0°, and aconventional trapezoidal distortion correction is performed.

In a case where the projection angle is greater than 0°, when image data2900 of 1920 pixels×1080 pixels is input (FIG. 32A), a range of 1280pixels×720 pixels that is the resolution of the display element 114 iscut out from the image data (image data 2901 illustrated in FIG. 32B).Then, for the image data of the cut-out range, a conventionaltrapezoidal distortion correction is performed (image data 2902illustrated in FIG. 32C). More specifically, in the horizontaldirection, the image data is corrected in a trapezoidal shape inaccordance with the projection angle as illustrated in FIG. 32C, and, inthe vertical direction, a distortion correction in which the height ofthe line increases in the vertical downward direction is performed.Then, image data after the correction is projected onto the projectionface, and, as illustrated in FIG. 32D, a projection image 2903 having arectangular shape is displayed. In such a case, while the distortion iscorrected in both the horizontal direction and the vertical directionfor the projection image, there are pixels not contributing to thedisplay.

FIGS. 33A to 33D are diagrams that illustrate examples of cutting out ofimage data, image data on a display element 114, and a projection imagein a case where the projection angle is greater than 0°, and thegeometric distortion correction (trapezoidal distortion correction)according to this first embodiment is performed.

In a case where the projection angle is greater than 0°, when image data3000 of 1920 pixels×1080 pixels is input (FIG. 33A), the memorycontroller 107, from this image data, cuts out image data of a range ofan area of a trapezoidal shape of a cut-out range according to theprojection angle from the image memory 101 (image data 3001 illustratedin FIG. 33B). Here, as the cut-out range, by the correction control unit108, the horizontal lower side is calculated as 1280 pixels, and thehorizontal upper side is calculated as a value acquired by multiplying1280 pixels by the reciprocal of the first correction coefficientaccording to the projection angle θ, and, as the range in the verticaldirection, a value acquired by multiplying the height of the input imagedata by the reciprocal of the second correction coefficient iscalculated.

Then, the memory controller 107 performs the geometric distortioncorrection for the image data of the cut-out range. More specifically,the memory controller 107, in the horizontal direction, as illustratedin FIG. 33C, corrects the image data in a trapezoidal shape according tothe projection angle, and, in the vertical direction, performs adistortion correction in which the height of the line increases in thedownward vertical direction. Here, as illustrated in FIG. 33B, since thememory controller 107 cuts out pixels corresponding to the area of thetrapezoidal shape according to the projection angle, an image of 1280pixels×720 pixels is expanded on the display element 114, and, asillustrated as a projection image 3003 in FIG. 33D, the cut-out area isprojected without being reduced.

As illustrated in the examples represented in FIGS. 33A to 33D, an imageof the unused area that originally remains after the cutting out of theinput image data is used for the area of the periphery of the image dataafter the geometric distortion correction (trapezoidal distortioncorrection), whereby the projection image is displayed, and the amountof information lacking in the area of the periphery in the horizontaldirection and the vertical direction is supplemented. Accordingly,compared to the conventional technique illustrated in FIGS. 32A to 32D,the image of the conventionally unused area can be effectively used,whereby effective use of the displayable area after the geometricdistortion correction (trapezoidal distortion correction) is realized.

Process of Projecting Image Data

Next, the flow of the process performed when an image according to theimage data is projected by the projector device 1 a will be described.FIG. 34 is a flowchart that illustrates the sequence of an imageprojection process according to the first embodiment.

In Step S100, in accordance with input of image data, various set valuesrelating to the projection of an image according to the image data areinput to the projector device 1 a. The input various set values, forexample, are acquired by the input control unit 119 and the like. Thevarious set values acquired here, for example, include a valuerepresenting whether or not the image according to the image data isrotated, in other words, whether or not the horizontal direction and thevertical direction of the image are interchanged, an enlargement rate ofthe image, and an offset angle θ_(ofst) at the time of projection. Thevarious set values may be input to the projector device 1 a as data inaccordance with the input of the image data to the projector device 1 aor may be input by operating the operation unit 14.

In next Step S101, image data corresponding to one frame is input to theprojector device 1 a, and the input image data is acquired by the memorycontroller 1032. The acquired image data is written into the imagememory 101.

In next Step S102, the image control unit 103 acquires the offset angleθ_(ofst). In next Step S103, the correction control unit 108 acquiresthe view angle α from the view angle control unit 106. In addition, innext Step S104, the correction control unit 108 acquires the projectionangle θ of the projection lens 12 from the rotation control unit 104.

In next Step S105, the image data cutting out and geometric distortioncorrection process are performed. Here, the image data cutting out andgeometric distortion correction process will be described in detail.FIG. 35 is a flowchart that illustrates the sequence of the image datacutting out and geometric distortion correction process according to thefirst embodiment.

First, in Step S301, the correction control unit 108 calculates thefirst correction coefficient using Equation (12). In next Step S302, thecorrection control unit 108 calculates the reduction rate of each linefrom the upper side (first side) to the lower side (second side) of theimage data using Equation (15). In addition, in Step S303, thecorrection control unit 108 acquires the second correction coefficientfor each line by using Equation (19) described above.

Then, next, in Step S304, the correction control unit 108 acquires thecut-out range based on the first correction coefficient and the secondcorrection coefficient as described above.

Next, in Step S305, the memory controller 107 cuts out image data of thecut-out range from the image data stored in the image memory 101. Then,in Step S306, the memory controller 107 performs the geometricdistortion correction described above for the image data of the cut-outrange using the first correction coefficient, the reduction rate, andthe second correction coefficient and ends the process.

Returning to FIG. 34, when the image data cutting out and geometricdistortion correction process are completed in Step S105, in Step S106,the overall control unit 120 determines whether or not an input of imagedata of a next frame of the image data input in Step S101 describedabove is present.

In a case where the input of the image data of the next frame isdetermined to be present, the overall control unit 120 returns theprocess to Step S101 and performs the processes of Steps S101 to S105described above for the image data of the next frame. In other words,the processes of Steps S101 to S105, for example, is repeated in unitsof frames of the image data in accordance with a verticalsynchronization signal VD of the image data. Accordingly, the projectordevice 1 a can cause each process to follow a change in the projectionangle θ in units of frames.

On the other hand, in Step S106, in a case where the image data of thenext frame is determined not to have been input, the overall controlunit 120 stops the image projecting operation in the projector device 1a. For example, the overall control unit 120 controls the light source111 so as to be turned off and issues an instruction for returning theposture of the drum unit 10 to be in the housed state to the rotationmechanism unit 105. Then, after the posture of the drum unit 10 isreturned to be in the housed state, the overall control unit 120 stopsthe fan cooling the light source 111 and the like.

As above, according to this first embodiment, in a case where thegeometric distortion correction is performed for the image data, aprojection image is displayed by using an image of the unused areaoriginally remaining after the cutting out of the input image data forthe area of the periphery of the image data after the geometricdistortion correction, and the amount of information lacking in the areaof the periphery in the horizontal direction and the vertical directionis supplemented. For this reason, according to this first embodiment,compared to a conventional technology, by effectively using the image ofthe unused area, the geometric distortion correction is performed forthe content of the projection image, and a high-quality projection imageeffectively using the displayable area can be acquired.

Particularly, in a case where, for example, environment video such asthe sky or the night sky is projected using the projector device 1 aaccording to this first embodiment, even in a case where the projectionimage is displayed in a trapezoidal shape, when the amount ofinformation to be displayed is large, a sense of presence can be moreeffectively acquired. In addition, in a case where a map image, or thelike is projected using the projector device 1 a according to thisembodiment, compared to a conventional technique, a relatively broadrange of peripheral information can be projected.

Modified Example of First Embodiment

According to the projector device 1 a of the first embodiment, ahorizontal distortion and a vertical distortion of the projection imagethat occur in accordance with the projection angle are eliminated by thegeometric distortion correction, and the amount of information issupplemented for both areas of the horizontal-direction area and thevertical-direction area. However, according to a modified example of thefirst embodiment, a horizontal distortion is eliminated by a geometricdistortion correction, and the amount of information is supplemented forthe horizontal-direction area, but a distortion correction is notperformed for the vertical direction.

The external appearance, the structure, and the functional configurationof the projector device 1 a according to the first embodiment describedabove may be applied to the modified example of the first embodiment.

In this modified example of the first embodiment, the correction controlunit 108 calculates the first correction coefficient used for ahorizontal distortion correction based on the projection angle inputfrom the rotation control unit 104 and the view angle input from theview angle control unit 106 by using Equation (12) described above andcalculates the reduction rate for each line by using Equation (15) butdoes not calculate the second correction coefficient used for a verticaldistortion correction.

In addition, based on the projection angle, the view angle, and thefirst correction coefficient, the correction control unit 108 determinesa cut-out range from the input image data such that image data after thegeometric distortion correction includes a displayable size of thedisplay device and outputs the determined cut-out range to the memorycontroller 107 and the extended function control unit 109.

The memory controller 107 cuts out (extracts) an image area of thecut-out range determined by the correction control unit 108 from thewhole area of a frame image relating to the image data stored in theimage memory 101 and outputs the image area that has been cut out asimage data.

In addition, the memory controller 107 performs a geometric distortioncorrection for the image data cut out from the image memory 101 by usingthe first correction coefficient and outputs the image data after thegeometric distortion correction to the image processor 102.

The flow of the process of projecting the image data according to themodified example of the first embodiment is similar to that of the firstembodiment described with reference to FIG. 34. In the modified exampleof the first embodiment, an image data cutting out and geometricdistortion correction process in Step S105 illustrated in FIG. 34 isdifferent from that of the first embodiment. FIG. 36 is a flowchart thatillustrates the sequence of the image data cutting out and geometricdistortion correction process according to the modified example of thefirst embodiment.

First, in Step S401, the correction control unit 108 calculates thefirst correction coefficient by using Equation (12). In next Step S402,the correction control unit 108 calculates the reduction rate of eachline from the upper side (first side) to the lower side (second side) ofthe image data by using Equation (15).

Then, next, in Step S403, the correction control unit 108 acquires acut-out range based on the first correction coefficient as describedabove.

Next, in Step S404, the memory controller 107 cuts out image data of thecut-out range from the image data stored in the image memory 101. Then,in Step S405, the memory controller 107 performs the geometricdistortion correction described above for the image data of the cut-outrange using the first correction coefficient and the reduction rate andends the process.

Next, an example of the cutting out of image data and the geometricdistortion correction performed by the geometric distortion correctionunit 100 according to this modified example of the first embodiment willbe described.

FIGS. 37A to 37D are diagrams that illustrate examples of cutting out ofimage data, image data on the display element 114, and a projectionimage in a case where the projection angle θ is greater than 0°, and thegeometric distortion correction according to this embodiment isperformed.

In a case where the projection angle θ is greater than 0°, when imagedata 3400 of 1920 pixels×1080 pixels is input (FIG. 37A), the memorycontroller 107, from this image data 3400, cuts out image data 3401 of arange of an area of a trapezoidal shape of a cut-out range according tothe projection angle from the image memory 101 (FIG. 37B). Here, as thecut-out range, by the correction control unit 108, the horizontal lowerside is calculated as 1280 pixels, and the horizontal upper side iscalculated as a value acquired by multiplying 1280 pixels by thereciprocal of the first correction coefficient according to theprojection angle.

Then, the memory controller 107 performs the geometric distortioncorrection for the image data 3401 of the cut-out range (FIG. 37C). Morespecifically, the memory controller 107, in the horizontal direction,corrects the image data in a trapezoidal shape according to theprojection angle, as illustrated as image data 3402 in FIG. 37C. Here,as illustrated in FIG. 37B, since the memory controller 107 cuts outpixels corresponding to the area of the trapezoidal shape according tothe projection angle, an image of 1280 pixels×720 pixels is expanded onthe display element 114, and, as represented as a projection image 3403in FIG. 37D, the cut-out area is projected without being reduced.

As above, according to this modified example of the first embodiment,the horizontal distortion is eliminated by the geometric distortioncorrection, and the amount of information is supplemented for thehorizontal-direction area, but the geometric distortion correction isnot performed for the vertical direction. Accordingly, not only the sameadvantages as those of the first embodiment are acquired, but theprocessing load of the correction control unit 108 can be reduced.

In the first embodiment and the modified example of the firstembodiment, the method has been described in which the projection angleis derived by changing the projection direction of the projection unitsuch that the projection unit is moved while projecting the projectionimage onto the projection face, and a correction amount used foreliminating the geometric distortion according to the projection angle θis calculated, but a change in the projection direction does not need tobe dynamic. In other words, as illustrated in FIGS. 14 and 15, thecorrection amount may be calculated using a fixed projection angle inthe stopped state.

In addition, the calculation of the correction amount and the detectionmethod are not limited to those described in this embodiment, and acut-out range including also an area other than the above-describedimage data area after the correction may be determined according to thecorrection amount.

Each of the projector devices 1 a according to the first embodiment andthe modified example of the first embodiment has a configuration thatincludes hardware such as a control device such as a CPU (CentralProcessing Unit), storage devices such as ROM (Read Only Memory) and RAM(Random Access Memory), an HDD (Hard Disk Drive), and an operation unit14.

In addition, the rotation control unit 104, the view angle control unit106, the image control unit 103 (and each unit thereof), the extendedfunction control unit 109, the geometric distortion correction unit 100(and each unit thereof), the input control unit 119, and the overallcontrol unit 120 mounted as circuit units of the projector devices 1 aof the first and the modified example of the first embodiment may beconfigured to be realized by software instead of being configured byhardware.

In a case where the projector device is realized by the software, animage projection program (including an image correction program)executed by the projector devices 1 a according to the first embodimentand the modified example of the first embodiment is built in ROM or thelike in advance and is provided as a computer program product.

The image projection program executed by the projector devices 1 aaccording to the first embodiment and the modified example of the firstembodiment may be configured to be recorded on a computer-readablerecording medium such as a compact disk-ROM (CD-ROM), a flexible disk(FD), a compact disk-R (CD-R), or a digital versatile disk (DVD) so asto be provided as a file having an installable form or an executableform.

In addition, the image projection program executed by the projectordevices 1 a according to the first embodiment and the modified exampleof the first embodiment may be configured to be stored in a computerconnected to a network such as the Internet and be provided by beingdownloaded through the network. In addition, the image projectionprogram executed by the projector devices 1 a according to the firstembodiment and the modified example of the first embodiment may beconfigured to be provided or distributed through a network such as theInternet.

The image projection program executed by the projector devices 1 aaccording to the first embodiment and the modified example of the firstembodiment has a module configuration including the above-describedunits (the rotation control unit 104, the view angle control unit 106,the image control unit 103 (and each unit thereof), the extendedfunction control unit 109, the geometric distortion correction unit 100(and each unit thereof), the input control unit 119, and the overallcontrol unit 120). As actual hardware, as the CPU reads the imageprojection program from the ROM and executes the read image projectionprogram, the above-described units are loaded into a main memory device,the rotation control unit 104, the view angle control unit 106, theimage control unit 103 (and each unit thereof), the extended functioncontrol unit 109, the geometric distortion correction unit 100 (and eachunit thereof), the input control unit 119, and the overall control unit120 are generated on the main storage device.

Second Embodiment

Next, a second embodiment will be described. In the projector devices 1and 1 a described above, when the projection angle is shifted from anangle perpendicular to the projection medium, the size of a projectionimage projected onto the projection medium becomes different from thatof a case where the projection angle is perpendicular to the projectionmedium. Accordingly, there is concern that an expected desiredprojection image cannot be acquired. An object of the second embodimentis to provide a projector device capable of suppressing a change in thesize of the projection image in a case where the projection angle ischanged.

Here, a change of a projection image according to a change in theprojection angle θ in a case where the above-described trapezoidaldistortion correction (keystone correction) is not performed will bedescribed with reference to FIG. 38. FIG. 38 illustrates an example inwhich the projection angle θ of a projection lens 12 is increased from aprojection angle θ=−90° by rotating a drum unit 10 of a projector device1 b disposed on a horizontal base 2 in a rotation direction denoted byan arrow 302 in the figure. At this time, it is assumed that a floor 6and a ceiling 4 are horizontal with respect to the base 2, and a wall 3is perpendicular to the base 2. In other words, when the projectionangle θ=0°, 90°, and −90°, the projection direction of the projectionlens 12 is perpendicular to the wall 3 and the ceiling 4.

In this case, at the projection angle of −90°, the projection directionof the projection lens 12 is perpendicular to the floor 6, and aprojection image 300 a having no distortion can be acquired. When theprojection angle θ is increased from −90°, like projection images 300 band 300 c, a trapezoidal distortion occurs in the projection image. Inother words, in the projection image, the front side is sequentiallylengthened toward a direction in which the projection angle θ increases,the rear side is further lengthened than the front side, and thevertical size also grows toward the direction in which the projectionangle θ increases.

When the projection angle θ is further increased, and the projectiondirection exceeds a boundary 7 between the floor 6 and the wall 3, tothe contrary to the case until then, the distortion decreases accordingto an increase in the projection angle θ, and the size of the projectionimage is decreased as well (projection images 300 d and 300 e). Then,when the projection angle θ=0°, the projection image 300 e having nodistortion is acquired. In the case illustrated in FIG. 38, a distancefrom the projector device 1 b to the projection image 300 e is longerthan a distance from the projector device 1 b to the projection image300 a. Accordingly, the projection image 300 e is projected in a sizelarger than that of the projection image 300 a. When the projectionangle θ is increased from 0°, like projection images 300 f and 300 g,the distortion increases according to an increase in the projectionangle θ, and the size of the projection image is increased as well.

When the projection angle θ is further increased, and the projectiondirection exceeds a boundary 5 between the wall 3 and the ceiling 4, tothe contrary to the case until then, the distortion decreases accordingto an increase in the projection angle θ, and the size of the projectionimage is decreased as well (projection images 300 h and 300 i). Then, atthe projection angle θ=90°, a projection image 300 j having nodistortion is acquired, and, when the projection angle θ is furtherincreased, the distortion increases according to an increase in theprojection angle θ, and the size of the projection image is increased aswell (a projection image 300 k).

FIG. 39 illustrates an example of a case where a trapezoidal distortioncorrection (keystone correction) according to an existing technology isperformed for a projection image in which a trapezoidal distortionoccurs as illustrated in FIG. 38. In the keystone correction accordingto the existing technology, a correction is performed such that theprojection image maintains the aspect ratio of the original image withrespect to a shorter side (hereinafter, referred to as a shorter side)of the upper base and the lower base of a trapezoidal shape distortedaccording to the projection angle θ. As illustrated in FIG. 38, theshorter side of the projection image in which the trapezoidal distortionoccurs is changed according to the projection angle θ. Accordingly, thesize of the projection image for which the keystone correction isperformed is changed according to the projection angle θ.

In the example illustrated in FIG. 39, for example, between theprojection direction of the projection angle θ=−90° and the direction ofthe boundary 7, according to changes in the lengths of the shorter sidesof projection images 300 a to 300 c for which the keystone correctionhas not been performed, the sizes of corrected projection images 301 a,301 b, and 301 c are increased according to an increase in theprojection angle θ. Between the direction of the boundary 7 and thedirection of the boundary 5, according to changes in the lengths of theshorter sides of projection images 300 d to 300 g for which thecorrection has not been performed, the sizes of corrected projectionimages 301 d to 301 g are changed. More specifically, according to anincrease in the projection angle θ, the sizes of the projection images301 d to 301 g are decreased between the direction of the boundary 7 andthe projection angle θ=0° and are increased between the projection angleθ=0° and the boundary 5. In addition, similarly, in a direction afterthe boundary 5, according to changes in the lengths of the shorter sidesof projection images 300 h to 300 k for which the correction has notbeen performed, the sizes of corrected projection images 301 h to 301 kare changed.

FIG. 40 is a diagram that illustrates an example of a change in thevertical-direction size of a projection image according to theprojection angle θ. In FIG. 40, a line 303 represents an example of achange in the height H according to the projection angle θ using a ratiowith respect to the height H₀ of the projection image of a case where adistance toward the projection direction for the projection medium isshortest. In this example, out of projection angles θ=0° and 90° atwhich the projection direction is perpendicular to the projectionmedium, in a case where the projection angle θ=90°, in other words, in acase where the projection direction is perpendicular to the ceiling 4,the distance toward the projection direction for the projection mediumis shortest. This projection angle θ at which the distance toward theprojection direction for the projection medium is shortest is denoted bya projection angle θ_(MIN).

As illustrated in FIG. 40, the height H of the projection image that isminimal in a case where the projection angle θ=90° is increased as theprojection angle θ decreases, and the projection direction becomescloser to the boundary 5 between the ceiling 4 and the wall 3. In thisexample, a projection angle θ=30° corresponds to the projectiondirection of the boundary 5. In the projection direction correspondingto the boundary 5, as the angle of the projection medium with respect tothe projection direction is discontinuous, a change in the height H withrespect to the projection angle θ is discontinuous.

In this way, in a case where the size of the projection image on theprojection medium changes according to the projection angle θ, when thedrum unit 10 is rotated, a projection image having a size different froman initial projection image is presented to the user, whereby there isconcern that the user feels discomfort. In order to solve this, in thissecond embodiment, a reduction process is performed for image data to beprojected in the vertical and horizontal directions such that the sizeof the projection image on the projection medium is constant atprojection angles θ.

The projector device 1 b, which has a functional configurationrepresented in FIG. 43 to be described later, according to this secondembodiment performs a keystone correction for a projection image of eachprojection angle θ. Then, in the second embodiment, the projector device1 b performs a reduction process for image data before the keystonecorrection such that the height H and the length W of the shorter sideof the projection image, for which the keystone correction has beenperformed, that is projected onto the projection medium coincide withthe height H (referred to as a height H₀) and the length W (referred toas a length W₀) of the shorter side of the projection image at theprojection angle θ_(MIN).

Here, in a case where the projection direction for the projection mediumis the projection angle θ_(MIN), the size of the projection imageprojected onto the projection medium is smallest of all the sizes of theprojection images of the case of being projected at projection angles θ.In the embodiment, the size of the projection image of which theprojection direction is each projection angle θ is reduced by performinga size correcting process with the size of the projection image of acase where the projection direction is the projection angle θ_(MIN)being set as the lower limit size.

More specifically, the projector device 1 b acquires a reduction rateR_(W)(θ) for the length W(θ) of the shorter side of the projection imagefor causing the size of the projection image of each projection angle θto coincide with the size of the projection image of the projectionangle θ_(MIN). In other words, the reduction rate R_(W)(θ), asrepresented in the following Equation (20), is each ratio of the lengthW(θ) of the shorter side of the projection image of each projectionangle θ to the horizontal-direction width W₀ of the projection image ofthe projection angle θ_(MIN) in a case where the keystone correction isnot performed. Then, by using this reduction rate R_(W)(θ), a reductionprocess is performed for the image data before the keystone correction.

R _(W)(θ)=W ₀ /W(θ)  (20)

A method of calculating the length W(θ) of the shorter side of theprojection image will be described with reference to FIGS. 41 and 42.FIG. 41 illustrates an example of a case where an image is projectedonto a projection medium having a projection face perpendicular to thewall 3, in other words, the projection direction of the projection angleθ=0°. In addition, FIG. 42 illustrates an example of a case where animage is projected onto a projection medium having a projection faceperpendicular to the ceiling 4, in other words, the projection directionof the projection angle θ=90°. In the cases illustrated in FIGS. 41 and42, the ceiling 4 is horizontal with respect to the base 2, and the wall3 is perpendicular to the base 2. In other words, in cases where theprojection angle θ=0° or 90°, the projection direction of the projectionlens 12 is perpendicular to the wall 3 and the ceiling 4.

Here, in a case where the size of the display element 114 is differentbetween the vertical direction and the horizontal direction, avertical-direction view angle α_(V) and a horizontal-direction viewangle α_(H) are defined as the view angle α. These view angles α_(V) andα_(H) are constant regardless of the projection angle θ. Hereinafter,angles of ½ of the view angle α_(V) and the view angle α_(H) arerepresented as an angle β_(V) and an angle β_(H), and description willbe presented using a view angle 2β_(V) and a view angle 2β_(H)

First, a case will be described in which the projection image isprojected onto the wall 3. In FIG. 41, a range h_(w) represents a rangefrom the upper side to the lower side of the projection image of a casewhere the projection image is projected onto the wall 3 at theprojection angle θ with the view angle 2β_(V). As described withreference to FIG. 38, in a case where the projection image is projectedonto the wall 3, for a projection angle θ>0°, the lower end of theprojection image, in other words, the range h_(w) forms the shorterside. Here, a distance (a distance of a case where the projectiondirection is perpendicular to the wall 3) up to the wall 3 of a casewhere the projection angle θ=0° is a distance r₀, and a distance up tothe wall 3 on the shorter side of the projection image at the projectionangle θ is a distance r_(w). In addition, in this case, the projectionangle θ is an angle within the range of 0° to a maximum projection anglefor which the lower end of the range h_(w) is caught in the wall 3. Inthis case, the relation between the distance r₀ and the distance r_(W)is represented in the following Equation (21).

r ₀ =r _(w)×cos(θ−β_(V))  (21)

Meanwhile, when the view angle α_(H) arrives at the projection angle θto be constant, the length W of the shorter side of the projection imagefor which the keystone correction has not been performed is proportionalto the distance r_(w) up to the projection medium toward the shorterside. Thus, a change in the length W(θ) according to the projectionangle θ of a case where the projection image is projected onto the wall3 is represented in the following Equation (22).

W(θ)=2r _(w)×tan β_(H)  (22)

By applying Equation (20) to Equation (21), as represented in thefollowing Equation (23), the length W(θ) can be calculated based on thedistance r₀ and the projection angle θ. In addition, in Equation (23)and Equation (21) described above, in a case where the projection angleθ>90° (for example, the projection image is projected onto a face facingthe wall 3 with the projector device 1 b being interposed therebetween),the sign of the angle β_(V) is positive.

W(θ)=2r ₀×tan β_(H)/cos(θ−β_(V))  (23)

Next, a case will be described in which the projection image isprojected onto the ceiling 4. In FIG. 42, a range h_(c) represents arange from the upper side to the lower side of the projection image of acase where the projection image is projected onto the ceiling at theprojection angle θ with the view angle 2β_(V). As described withreference to FIG. 38, in a case where the projection image is projectedonto the ceiling 4, a side of the projection image, in other words, therange h_(c) that is close to the projector device 1 b forms the shorterside. Here, a distance (a distance of a case where the projectiondirection is perpendicular to the ceiling 4) up to the ceiling 4 of acase where the projection angle θ=90° is a distance r₉₀, and a distanceup to the ceiling 4 on the shorter side of the projection image at theprojection angle θ is a distance r_(c). In addition, in this case, theprojection angle θ is an angle within a range in which the shorter sideof the range h_(c) is caught in the ceiling 4. In this case, therelation between the distance r₉₀ and the distance r_(c) is representedin the following Equation (24).

r ₉₀ =r _(c)×sin(θ+β_(V))  (24)

Meanwhile, when the view angle α_(H) arrives at the projection angle θto be constant, the length W of the shorter side of the projection imagefor which the keystone correction has not been performed is proportionalto the distance r_(w) up to the projection medium toward the shorterside. Thus, a change in the length W(θ) according to the projectionangle θ of a case where the projection image is projected onto theceiling 4 is represented in the following Equation (25) that is similarto Equation (22) described above.

W(θ)=2r _(c)×tan β_(H)  (25)

By applying Equation (24) to Equation (25), as represented in thefollowing Equation (26), the length W(θ) can be calculated based on thedistance r₉₀ and the projection angle θ. In addition, in Equation (26)and Equation (24) described above, in a case where the projection angleθ>90°, the sign of the angle β_(V) is negative.

W(θ)=2r ₉₀×tan β_(H)/sin(θ+β_(V))  (26)

Internal Configuration of Projector Device According to SecondEmbodiment

FIG. 43 is a block diagram that illustrates an example of the functionalconfiguration of the projector device 1 b according to the secondembodiment. In FIG. 43, the same reference numeral is assigned to aportion common to the configuration illustrated in FIG. 4 describedabove, and detailed description thereof will not be presented.

The external appearance and the structure of the projector device 1 baccording to the second embodiment are similar to those of the firstembodiment.

As illustrated in FIG. 43, the image processing/controlling unit 90illustrated in FIG. 4 includes: an image memory 101; an imagecutting-out unit 1100; an image processor 1102; and an image controlunit 1103. In addition, a CPU 1120 realizes the function of an overallcontrol unit 120 according to a program stored in ROM in advance withRAM operated as a work memory. In the example illustrated in FIG. 43,the output of an operation unit 14 is supplied to the CPU 1120.

In addition, as illustrated in FIG. 43, in the projector device 1 b, adistance sensor 60 and a distance measurement unit 1107 are added to theprojector device 1 illustrated in FIG. 4. The distance sensor 60 isdisposed in a window portion 13 for measuring a distance from aprojection lens 12 to a projection medium. A detection signal outputfrom the distance sensor 60 is input to the distance measurement unit1107. In addition, angle information representing the angle of a drumunit 10, in other words, the projection direction according to aprojection lens 12 is input from a rotation control unit 104 to thedistance measurement unit 1107. The distance measurement unit 1107performs a distance measurement process based on the detection signal,thereby derives a distance from the distance sensor 60 to the projectionmedium in the projection direction represented in the angle information.

In addition, the distance measurement unit 1107 calculates a projectiondirection that is perpendicular to the projection medium based on thederived distance. The angle of the calculated projection directionperpendicular to the projection medium with respect to the projectionangle 0° is set as a projection angle θref (first direction).

Processes performed by an image processor 1102 and an image control unit1103 to be described later are performed based on this projection angleθ_(ref). In other words, by correcting the projection angle θ by usingthe projection angle θ_(ref), also in a case where the horizontaldirection (projection angle 0°) of the projector device 1 b is notperpendicular to the projection face of the projection medium, processesdepending on the projection angle θ can be appropriately performed bythe image processor 1102 and the image control unit 1103. A method ofcalculating the projection angle θ_(ref) will be described later.

Image data output from the image cutting-out unit 1100 and theprojection angle θ_(ref) acquired by the distance measurement unit 1107are supplied to the image processor 1102. The image processor 1102outputs the image data for which image processing has been performedbased on timing represented in a vertical synchronization signal VDsupplied from a timing generator not illustrated in the figure.

The image processor 1102, for example, performs image processing for thesupplied image data, for example, by using an image memory 101. Theimage processor 1102 accesses the image memory 101 through the imagecutting-out unit 1100. However, the embodiment is not limited thereto,and a memory used by the image processor 1102 for the image processingmay be separately arranged.

For example, the image processor 1102 performs a size converting processsuch that the size of the image data supplied from the image cutting-outunit 1100 coincides with the size of the display element 114. Inaddition, the image processor 1102 may perform various kinds of imageprocessing such as a size converting process executed through a generallinear transformation process, an interpolation process, a thinning outprocess, an edge enhancement process, a low pass filter process, and ahalftone mixing process described for the image processing/controllingunit 90 illustrated in FIG. 4. The image data output from the imageprocessor 1102 is supplied to the display element 114.

The image control unit 1103 designates an image cut-out area using theimage cutting-out unit 1100 based on the information relating to theangle supplied from the rotation control unit 104, the projection angleθ_(ref) supplied from the distance measurement unit 1107, and theinformation relating to the view angle supplied from the view anglecontrol unit 106.

At this time, the image control unit 1103 designates a cut-out area ofthe image data based on a line position according to an angle betweenprojection directions before and after the change of the projection lens12. The image control unit 1103 designates the image cut-out area forthe image cutting-out unit 1100. In addition, the image control unit1103 instructs the image cutting-out unit 1100 to read image data fromthe designated image cut-out area in synchronization with a verticalsynchronization signal VD supplied from a timing generator notillustrated in the figure.

In the description presented above, while the image cutting-out unit1100, the image processor 1102, the image control unit 1103, therotation control unit 104, the view angle control unit 106, and thedistance measurement unit 1107 have been described as separate hardware,the configuration is not limited to this example. For example, each ofthese units may be realized by a module of a program operating on theCPU 1120.

Size Correcting Process Relating to Second Embodiment

Next, the flow of the image projecting process performed by theprojector device 1 b that can be applied to the second embodiment willbe described with reference to a flowchart represented in FIG. 44.

First, in Step S500, the distance measurement unit 1107 acquires aprojection angle θ for which the projection direction is perpendicularto the projection medium as the reference angle θ_(ref) at the time ofprojection. In addition, the distance measurement unit 1107 acquires aprojection angle θ_(MIN) corresponding to a projection direction inwhich a distance up to the projection medium is shortest. Methods ofacquiring the reference angle θ_(ref) and the projection angle θ_(MIN)will be described later.

In the next Step S501, in accordance with the input of the image data,various set values relating to the projection of an image according tothe image data are input to the projector device 1 b. The various setvalues that have been input, for example, are acquired by the CPU 1120.The various set values acquired here, for example, include a valuerepresenting whether or not the image according to the image data isrotated, in other words, whether or not the horizontal direction and thevertical direction of the image are interchanged, an enlargement rate ofthe image, and an offset angle θ_(ofst) at the time of projection. Thevarious set values may be input to the projector device 1 b as data inaccordance with the input of the image data to the projector device 1 bor may be input by operating the operation unit 14.

In the next Step S502, image data corresponding to one frame is input tothe projector device 1 b, and the input image data is acquired by theimage cutting-out unit 1100. The acquired image data is written into theimage memory 101.

In the next Step S503, the image control unit 1103 acquires the offsetangle θ_(ofst). In the next Step S504, the image control unit 1103acquires the cut out size, in other words, the size of the cut-out areaof the input image data. The image control unit 1103 may acquire thesize of the cut-out area from the set value acquired in Step S501 or maybe acquired according to an operation for the operation unit 14. In thenext Step S505, the image control unit 1103 acquires the view angle α ofthe projection lens 12. For example, the image control unit 1103acquires the vertical-direction view angle α_(V) and thehorizontal-direction view angle α_(H) of the projection lens 12 from theview angle control unit 106. The image control unit 1103 may beconfigured to acquire only one of the view angle α_(V) and the viewangle α_(H) from the view angle control unit 106 and acquire the otherview angle from the one view angle that has been acquired according tothe aspect ratio of the display element 114.

In addition, in the next Step S506, the distance measurement unit 1107acquires the projection angle θ of the projection lens 12, for example,from the rotation control unit 104. The distance measurement unit 1107corrects the acquired projection angle θ by using the reference angleθ_(ref) acquired in Step S500, thereby acquiring a corrected projectionangle θ′. This projection angle θ′ is transmitted to the image processor1102 and the image control unit 1103.

In the next Step S507, the image control unit 1103 acquires a cut-outarea of the input image data by using Equations (3) to (8) describedabove based on the offset angle θ_(ofst), the size of the cut-out area,the view angle α, and the projection angle θ′ corrected by the distancemeasurement unit 1107 that are acquired in Steps S503 to S506. The imagecontrol unit 1103 instructs the image cutting-out unit 1100 to readimage data from the acquired cut-out area. The image cutting-out unit1100 reads image data within the cut-out area from the image data storedin the image memory 101 according to an instruction transmitted from theimage control unit 1103, thereby performing cutting out of the imagedata. The image cutting-out unit 1100 supplies the image data of thecut-out area read from the image memory 101 to the image processor 1102.

In Step S508, the image processor 1102 performs a size convertingprocess, for example, by using Equations (1) and (2) described above forthe image data supplied from the image cutting-out unit 1100. Inaddition, the image processor 1102, for the image data, performs areduction process using the reduction rate R_(W)(θ) acquired in aprocess to be described later and a keystone correction according to theprojection angle θ′ corrected by the distance measurement unit 1107.

The image data for which the size converting process, the reductionprocess and the keystone correction have been performed by the imageprocessor 1102 is supplied to the display element 114. The displayelement 114 modulates light supplied from a light source 111 accordingto the image data and emits the modulated light. The emitted light isprojected from the projection lens 12.

In the next Step S509, the CPU 1120 determines whether or not there isan input of image data of the next frame of the image data input in StepS502 described above. In a case where it is determined that there is aninput of the image data of the next frame, the CPU 1120 returns theprocess to Step S502 and performs the processes of Steps S502 to S508described above for the image data of the next frame. In other words,the processes of Steps S502 to S508, for example, is repeated in unitsof frames of the image data according to the vertical synchronizationsignal VD of the image data. Thus, the projector device 1 b can causeeach process to follow a change in the projection angle θ in units offrames.

On the other hand, in Step S509, in a case where it is determined thatthe image data of the next frame has not been input, the CPU 1120 stopsthe image projecting operation of the projector device 1 b. For example,the CPU 1120 performs control of the light source 111 to be in the Offstate and instructs a rotation mechanism unit 105 to return the postureof the drum unit 10 to the initial posture. Then, after the posture ofthe drum unit 10 is returned to the initial posture, the CPU 1120 stopsa fan that cools the light source 111 and the like.

FIG. 45 is a flowchart that illustrates the flow of a keystonecorrection and a reduction process according to the second embodiment.The process according to the flowchart illustrated in FIG. 45 isincluded in the process of Step S508 represented in FIG. 44 describedabove.

The image processor 1102 acquires a reduction rate R_(W)(θ) for theprojection angle θ acquired in Step S506 according to Equations (20) to(26) described above in Step S600. Actually, the image processor 1102acquires a reduction rate R_(W)(θ′) for the projection angle θ′ acquiredby correcting the projection angle θ using the reference angle θ_(ref).For example, the projection angle θ′ is applied to the variable θ of thereduction rate R_(W)(θ) acquired by using Equations (20) to (26).

In the next Step S601, the image processor 1102 performs a reductionprocess according to the reduction rate R_(W)(θ′) acquired in Step S600for the image data supplied from the image cutting-out unit 1100. Inaddition, in the next Step S602, the image processor 1102 performs akeystone correction according to the projection angle θ′ for the imagedata for which the reduction process has been performed in Step S601.

The processes of Steps S601 and S602 are performed by the imageprocessor 1102 by using a predetermined area of the memory 101. It isapparent that a memory that is dedicatedly used for image processing maybe arranged in the image processor 1102.

Then, in the next Step S603, the image processor 1102 outputs the imagedata for which the reduction process and the keystone correction havebeen performed to the display element 114. The light, which is based onthe image data, output from the display element 114 is projected ontothe projection medium at the projection angle θ′ from the projectionlens 12. A projection image having the same size as the projection imageat the time of being projected at the projection angle θ_(MIN) isprojected onto the projection medium.

The processes of Steps S601 and S602 described above will be describedmore specifically with reference to FIGS. 46A and 46B. Here, byreferring to FIG. 38 described above, the reference angle θ_(ref)=0°,and the projection direction is perpendicular to the projection medium(the wall 3) at the projection angle θ=0°. In addition, it is assumedthat the distance up to the projection medium is shortest at theprojection angle θ=90°.

FIG. 46A illustrates an example of the image data projected onto theceiling 4 with the projection angle θ=90° (=projection angle θ_(MIN)).In addition, FIG. 46B illustrates an example of the image data projectedonto the ceiling 4 with a projection angle θ_(a) that is smaller thanthe projection angle θ=90°. Here, when the projection direction for theboundary 5 between the ceiling 4 and the wall 3 is the projection angleθ_(M), it is assumed that the projection angle θ_(a) satisfiesθ_(MIN)>θ_(a)>θ_(M). In addition, the projection angle θ_(a) iscorrected by using the reference angle θ_(ref)

In FIGS. 46A and 46B, examples of projection images 300 j and 300 i of acase where the keystone correction and the reduction process have notbeen performed are illustrated on the left side. In addition, in FIGS.46A and 46B, examples of image data for which the reduction process hasbeen performed in Step S601 are illustrated at the center, and examplesof image data for which the keystone correction has been performed inStep S602 are illustrated on the right side.

In the example of the projection angle θ_(MIN) illustrated in FIG. 46A,in a case where the projection direction is perpendicular to theprojection medium, and a trapezoidal distortion does not occur, theprojection images 300 j has a size that is the reference for thereduction process. Thus, the image processor 1102 does not perform thereduction process of Step S601 and acquires image data 310 a having asize coinciding with the size of the original image data. In addition,since a trapezoidal distortion does not occur in the image data 310 a,the image processor 1102 does not perform the keystone correction ofStep S602. Accordingly, image data 310 a′ having the size and the shapeof the image coinciding with those of the image data 310 a is suppliedto the display element 114.

In the example of the projection angle θ_(a) illustrated in FIG. 46B,the projection direction is not perpendicular to the projection medium,and a trapezoidal distortion occurs, and the length W of the shorterside of a trapezoid according to a projection image is differentaccording to the projection angle θ. Thus, in this example of theprojection angle θ_(a), it is necessary to perform the reduction processof Step S601 and the keystone correction of Step S602 for the image datasupplied to the display element 114.

In the example illustrated in FIG. 46B, in the projection image, thelength W of the shorter side of a trapezoid according to a trapezoidaldistortion changes (grows) according to the projection angle θ_(a) basedon Equation (26) described above. Thus, the image processor 1102acquires a reduction rate R_(W)(θ_(a)) using Equations (20) to (26) bythe process of Step S601 and performs a reduction process according tothe reduction rate R_(W)(θ_(a)) for the image data supplied from theimage cutting-out unit 1100 for the horizontal and vertical directions.Accordingly, reduced image data 310 b having the same aspect ratio asthat of the original image data is generated.

The image processor 1102 performs a keystone correction according to theprojection angle θ, for the reduced image data 310 b by using anexisting technology by the process of Step S602. The image data 310 b′for which the reduction process and the keystone correction have beenperformed is formed in a trapezoidal shape in which the length of theupper base is reduced according to the trapezoidal distortion and thereduction rate R_(W)(θ_(a)), and the length of the lower base is reducedwith the reduction rate R_(W)(θ_(a)) according to the projection angleθ_(a). As described above, the keystone correction is a correction formaintaining the aspect ratio of the original image by using the length Wof the lower base of the trapezoidal shape as the reference. Thus, for aprojection image acquired by projecting the image data 310 b′ onto theprojection medium (the ceiling 4) according to the projection angleθ_(a), a trapezoidal distortion occurring according to the projectionangle θ_(a) is corrected, and the size coincides with the size of theprojection image according to the projection angle θ_(MIN).

As above, according to the second embodiment, a projection imageconstantly having the same size and the same shape regardless of theprojection angle θ can be acquired.

Modified Example of Second Embodiment

Next, a modified example of the second embodiment will be described. Inthe second embodiment described above, by performing the keystonecorrection after the reduction process, the size correcting process isperformed. In contrast to this, in the modified example of the secondembodiment, by performing a reduction process after a keystonecorrection, the size correcting process is performed. In addition, thewhole flow of the size correcting process according to the modifiedexample of the second embodiment is common to that of the flowchartillustrated in FIG. 44 described above, and thus, description thereofwill not be presented.

FIG. 47 is a flowchart that illustrates the flow of the keystonecorrection and the reduction process according to the modified exampleof the second embodiment. The process according to the flowchartillustrated in FIG. 47 is included in the process of Step S508represented in FIG. 44 described above.

The image processor 1102 acquires a reduction rate R_(W)(θ) for theprojection angle θ acquired in Step S506 according to Equations (20) to(26) described above in Step S610. Actually, the image processor 1102acquires a reduction rate R_(W)(θ′) for the projection angle θ′ acquiredby correcting the projection angle θ using the reference angle θ_(ref).For example, the projection angle θ′ is applied to the variable θ of thereduction rate R_(W)(θ) acquired by using Equations (20) to (26).

In the next Step S611, the image processor 1102 performs a keystonecorrection according to the projection angle θ′ for image data suppliedfrom the image cutting-out unit 1100. In the next Step S612, the imageprocessor 1102 performs a reduction process according to the reductionrate R_(W)(θ′) for the image data for which the keystone correction hasbeen performed in Step S611. The image processor 1102 performs thekeystone correction of Step S611 in consideration of the reductionprocess of Step S612.

The processes of Steps S611 and S612 are performed by the imageprocessor 1102 by using a predetermined area of the image memory 101. Itis apparent that a memory that is dedicatedly used for image processingmay be arranged in the image processor 1102.

Then, in the next Step S613, the image processor 1102 outputs the imagedata for which the reduction process and the keystone correction havebeen performed to the display element 114. The light, which is based onthe image data, output from the display element 114 is projected ontothe projection medium at the projection angle θ′ from the projectionlens 12. A projection image having the same size as the projection imageat the time of being projected at the projection angle θ_(MIN) isprojected onto the projection medium.

The processes of Steps S611 and S612 described above will be describedmore specifically with reference to FIGS. 48A and 48B. Here, byreferring to FIG. 38 described above, the reference angle θ_(ref)=0°,and the projection direction is perpendicular to the projection medium(the wall 3) at the projection angle θ=0°. In addition, it is assumedthat the distance up to the projection medium is shortest at theprojection angle θ=90°.

FIG. 48A illustrates an example of the image data projected onto theceiling 4 with the projection angle θ=90° (=projection angle θ_(MIN)) Inaddition, FIG. 48B illustrates an example of the image data projectedonto the ceiling 4 with a projection angle θ_(b) that is smaller thanthe projection angle θ=90°. Here, when the projection direction for theboundary 5 between the ceiling 4 and the wall 3 is the projection angleθ_(M), it is assumed that the projection angle θ_(b) satisfiesθ_(MIN)>θ_(b)>θ_(M). In addition, the projection angle θ_(b) iscorrected by using the reference angle θ_(ref).

In FIGS. 48A and 48B, examples of projection images 300 j and 300 i of acase where the keystone correction and the reduction process have notbeen performed are illustrated on the left side. In addition, in each ofFIGS. 48A and 48B, an example of image data for which the keystonecorrection has been performed in Step S611 is illustrated at the center,and an example of image data for which the reduction process correctionhas been performed in Step S612 is illustrated on the right side.

In the example of the projection angle θ_(MIN) illustrated in FIG. 48A,in a case where the projection direction is perpendicular to theprojection medium, and a trapezoidal distortion does not occur, theprojection images 300 j has a size that is the reference for thereduction process. Thus, the image processor 1102 does not perform thekeystone correction of Step S611 and acquires image data 311 a having asize and a shape coinciding with those of the original image data. Inaddition, a trapezoidal distortion does not occur in the image data 311a, the size coincides with the size of the original image data, andaccordingly, the image processor 1102 does not perform a reductionprocess of Step S612. Accordingly, image data 311 a′ having the size andthe shape coinciding with those of the image data 311 a is supplied tothe display element 114.

In the example of the projection angle θ_(b) illustrated in FIG. 48B,the projection direction is not perpendicular to the projection medium,and a trapezoidal distortion occurs, and the length W of the shorterside of a trapezoid according to a projection image is differentaccording to the projection angle θ. Thus, in this example of theprojection angle θ_(b), it is necessary to perform the keystonecorrection of Step S611 and the reduction process of Step S612 for theimage data supplied to the display element 114.

The image processor 1102 performs the keystone correction according tothe projection angle θ_(b) by using an existing technology for imagedata supplied from the image cutting-out unit 1100 by the process ofStep S611. The image data 311 b for which the keystone correction hasbeen performed has a trapezoidal shape in which the length of the upperbase is reduced, the height is reduced according to the trapezoidaldistortion, the length of the lower base is the same as the length ofthe lower base of an image according to the original image data, thelength of the upper base is shorter than the length of the lower base,and the height is lower than the height of the image according to theoriginal image data.

The image processor 1102 performs the reduction process of Step S612 forthe image data 311 b for which the keystone correction has beenperformed. In the projection image, based on Equation (26) describedabove, the length W of the shorter side of a trapezoid according to thetrapezoidal distortion changes (grows) according to the projection angleθ_(b). Thus, the image processor 1102 acquires a reduction rateR_(W)(θ_(b)) using Equations (20) to (26). Then, the image processor1102 performs a reduction process according to the reduction rateR_(W)(θ_(b)) in the horizontal and vertical directions for the imagedata 311 b for which the keystone correction has been performed.Accordingly, in the embodiment, image data 311 b′ similar to the imagedata 310 b′ illustrated in FIG. 46B can be acquired.

In addition, the image processor 1102, in Step S611 described above,performs the keystone correction in consideration of the reduced sizeaccording to the reduction process performed in Step S612. For example,it may be considered to multiply the right side of Equation (26) appliedto the case illustrated in FIG. 48B by a coefficient that is “1” at theprojection angle θ=90° and changes according to the projection angle θ.

As above, also according to the modified example of the embodiment, aprojection image constantly having the same size and the same shaperegardless of the projection angle θ can be acquired.

Method of Measuring Distance Common to Second Embodiment and ModifiedExample of Second Embodiment

As described above, in the embodiment, it is necessary to acquire ashortest distance r_(MIN) from the projector device 1 b to theprojection medium and a projection angle θ_(MIN) at which the distancer_(MIN) is acquired. Hereinafter, regarding a method of measuring adistance that can be applied to be common to the embodiment and themodified example of the embodiment, two methods will be described.

First Distance Measurement Method

First, a first distance measurement method will be described. Accordingto the first method, a distance from a projection medium is measured byusing the distance sensor 60 while rotating the drum unit 10, whereby achange in the distance according to the projection angle θ is acquired.The distance measurement unit 1107 acquires a projection direction withrespect to two intersections of the projection media intersecting theprojection direction, which is perpendicular to the projection medium,based on an inflection point of the change in the distance and acquiresprojection angles θ of such projection directions.

The description will be presented with reference to FIG. 49. FIG. 49illustrates a case where the base 2 on which the projector device 1 b isdisposed is inclined with respect to the horizontal direction in thenegative direction of rotation of the drum unit 10. In such a state, forexample, while the drum unit 10 of the projector device 1 b is rotatedfrom the projection angle θ=0° in the counterclockwise direction,distances up to the wall 3 and the ceiling 4 that are projection mediaare measured by using the distance sensor 60. The distance measurementunit 1107 acquires a distance r at a projection angle θ based on adetection signal output from the distance sensor 60 and angleinformation supplied from the rotation control unit 104. In the exampleillustrated in FIG. 49, acquisition of a distance r_(st) at theprojection angle θ=0° is illustrated.

In FIG. 49, a distance r₀ represents a distance of a case where theprojection direction is perpendicular to the wall 3, and a distance r₁represents a distance of a case where the projection direction isperpendicular to the ceiling 4. In addition, a distance r_(M) is adistance at the boundary 5. As can be understood from FIG. 49, since theprojector device 1 b is inclined in the negative direction of therotation of the drum unit 10, the distance r_(st) is longer than thedistance r₀. In addition, an angle formed by the projection direction ofa case where the projection angle θ=0° and the projection directionperpendicular to the wall 3 is denoted as angle θ_(ref), and aprojection direction at the projection angle θ_(M) coincides with theboundary 5.

For example, the distance measurement unit 1107 takes in a detectionsignal output from the distance sensor 60 for every predeterminedinterval of the angle (the projection angle θ) represented by the angleinformation supplied from the rotation control unit 104 and calculates adistance r based on the detection signal that has been taken in. Then,an inflection point of a change of the calculated distance r accordingto the projection angle θ is acquired. In the example illustrated inFIG. 27, a distance r up to the wall 3 approximately changes accordingto the reciprocal of cos θ with respect to the projection angle θ. Inaddition, a distance r up to the ceiling approximately changes accordingto the reciprocal of sin θ with respect to the projection angle θ.

FIG. 50 schematically illustrates a change in the distance r withrespect to the projection angle θ in the example illustrated in FIG. 49.The distance r gradually decreases from the projection angle θ=0°according to the reciprocal of cos θ, the distance r up to the wall 3 isshortest (distance r_(MIN)) at a point at which the projection directionis perpendicular to the wall 3, and thereafter, the distance rincreases. Accordingly, this projection direction corresponds to aninflection point of the change in the distance r. This inflection pointis an inflection point of a downward projection. The distancemeasurement unit 1107 detects the inflection point of the downwardprojection based on a change in the distance r and acquires a projectionangle θ_(ref) corresponding to the detected inflection point.

When the projection angle θ is increased from the inflection point, ameasurement point for the wall 3 of the distance r is moved upward andarrives at the boundary 5 between the wall 3 and the ceiling 4. At thisboundary 5, the direction of the change in the distance r changes, and,when the projection angle θ is further increased, the distance rgradually decreases according to the reciprocal of sin θ. Accordingly,the projection angle θ_(M) at which the projection direction correspondsto the boundary 5 is an inflection point of the distance r. Thisinflection point is an inflection point of an upward projection. Thedistance measurement unit 1107 detects the inflection point of theupward projection based on a change in the distance r and acquires aprojection angle θ_(M) corresponding to the detected inflection point.

After the boundary 5, the distance r gradually decreases according to anincrease in the projection angle θ, the distance r up to the ceiling 4is shortest (distance r₁) at a point at which the projection directionis perpendicular to the ceiling 4, and thereafter, the distance rincreases. Accordingly, this projection direction is an inflection pointof the change in the distance r. This inflection point, similar to theinflection point at the projection angle θ_(ref) described above, is aninflection point of a downward projection. The distance measurement unit1107 detects the inflection point of the downward projection based on achange in the distance r. When the angle formed by the wall 3 and theceiling 4 is 90°, a projection angle θ corresponding to the inflectionpoint of the downward projection detected here is 90°+θ_(ref).

As above, based on a result of the distance measurement performedaccording to the rotation of the drum unit 10, the distance measurementunit 1107 detects two inflection points of downward projections and oneinflection point of the upward projection and acquires projection anglesθ corresponding thereto. For example, the distance measurement unit 1107performs the inflection point detecting operation described above as aninitial operation at the time of start-up of the projector device 1 band acquires projection angles θ at the inflection points in advance.However, the operation is not limited thereto, but the inflection pointdetecting operation described above may be performed according to auser's operation for the operation unit 14.

The distance measurement unit 1107 acquires distances up to theprojection medium for inflection points of the downward projectionsacquired as above and selects a shortest distance r_(MIN) from among theacquired distances. In addition, the distance measurement unit 1107acquires a projection angle θ_(MIN) corresponding to the inflectionpoint for which the shortest distance r_(MIN) is acquired. The distancemeasurement unit 1107 transmits the distance r_(MIN) and the projectionangle θ_(MIN) acquired as above to the image processor 1102.

In addition, when an image according to actual image data is projected,the distance measurement unit 1107, for example, corrects anglesrepresented in the angle information output from the rotation controlunit 104 by using the projection angle θ_(ref) acquired in advance andtransmits a resultant angle to the image processor 1102 as a projectionangle θ′ representing the projection direction.

In addition, as described above with reference to FIG. 38, the directionof a trapezoidal distortion of the projection image changes betweenbefore and after the projection directions corresponding to theprojection angles θ=−90°, 0°, and 90° and the boundaries 5 and 7. Thus,the image processor 1102 needs to change the side used as the referencefor the keystone correction to the upper base and the lower base of thetrapezoidal shape before and after such projection directions.

Thus, the distance measurement unit 1107 transmits informationrepresenting the side used as the reference for the keystone correctionto the image processor 1102 together with the projection angle θ′ basedon the angles represented in the angle information output from therotation control unit 104 and the projection angle θ corresponding toeach inflection point acquired in advance. The image processor 1102performs the keystone correction for the image data based on theprojection angle θ′ and the information representing the side used asthe reference.

In addition, the distance measurement unit 1107 transmits the projectionangle θ′ described above also to the image control unit 1103. The imagecontrol unit 1103 designates an image area to be cut out by the imagecutting-out unit 1100 in accordance with the projection angle θ′.

In the description presented above, while an example in which there isonly one boundary 5 between the wall 3 and the ceiling 4 has beendescribed, this first distance measurement method can respond to a casewhere a plurality of boundaries such as boundaries 5 a, 5 b, and 5 cillustrated in FIG. 51 are included. For example, by differentiating thechange in the projection angle θ of the distance r, an inflection pointcorresponding to the projection angle θ for which the projectiondirection is perpendicular to the projection medium and inflectionpoints corresponding to the boundaries 5 a, 5 b, and 5 c can bediscriminated from each other.

In addition, in the description presented above, while one distancesensor 60 is disposed in the drum unit 10, the number of distancesensors is not limited to this example. In other words, as illustratedin FIG. 52 as an example, a plurality of distance sensors 60 a, 60 b, 60c, and 60 d may be disposed in the drum unit 10. In the exampleillustrated in FIG. 52, four distance sensors 60 a, 60 b, 60 c, and 60 dare disposed at an angle interval of 90° in the drum unit 10, and windowportions 13 a, 13 b, 13 c, and 13 d are disposed in correspondence withthe distance sensors 60 a, 60 b, 60 c, and 60 d. In a case where onlyone distance sensor 60 described above is used, when each inflectionpoint is detected, it is necessary to rotate the drum unit 10, forexample, in an angle range of 270° from the projection angle θ=−90° ofthe initial state to the projection angle θ=180°. In contrast to this,in the example illustrated in FIG. 52, distance measurement of theentire periphery of 360° can be covered by rotation of the drum unit 10at most in an angle range of 90°, and accordingly, each inflection pointcan be acquired at a higher speed. It is apparent that the number of thedistance sensors 60 is not limited to four, but the number of distancesensors may be two or three, or five or more, and the interval of eachdistance sensor 60 is not limited to 90°.

Second Distance Measurement Method

Next, a second distance measurement method will be described. In thesecond distance measurement method, distances up to two arbitrary pointson a projection medium are measured by using the distance sensor 60.Then, based on the measured distances of the two points and an angleformed by projection directions for the two points, a projection angleθ_(ref0) for which the projection direction is perpendicular to theprojection medium is acquired.

A more specific description will be presented with reference to FIG. 53.The installation state and the like of the projector device 1 b aresimilar to those illustrated in FIG. 49 described above. First, thedistance measurement unit 1107 measures a distance a based on adetection signal acquired by the distance sensor 60 for an appropriateprojection angle θ₁ for which the projection direction faces the wall 3.Next, the distance measurement unit 1107 measures a distance b for aprojection angle θ₂ other than the projection angle θ₁. In addition, thedistance measurement unit 1107 calculates a differential angle Δθbetween the projection angle θ₁ and the projection angle θ₂.

In addition, the rotation of the drum unit 10 for the projection anglesθ₁ and θ₂, for example, is designated by a user operating the operationunit 14 while checking the projection direction. However, thedesignation is not limited thereto, but the rotation may be designatedby the distance measurement unit 1107 at predetermined timing such asthe timing of an initial operation.

The distance measurement unit 1107 acquires a differential angle ψbetween the projection angle θ₂ and the projection angle θ_(ref0) (firstdirection) for which the projection direction is perpendicular to theprojection medium by using the acquired distances a and b and the angleΔθ.

First, when a distance up to the projection medium (the wall 3) for theprojection angle θ_(ref0) is r₀, the following Equations (27) and (28)are satisfied for the distances a and b.

r ₀ =a×cos ψ  (27)

r ₀ =b×cos(Δθ+ψ)  (28)

By applying an addition theorem to the right side of “a×cosψ=b×cos(Δθ+ψ)”, the following Equation (29) is acquired, and, by solvingEquation (19) with respect to the distance a, Equation (30) is acquired.

a×cos ψ=b(cos Δθ cos ψ−sin Δθ sin ψ)  (29)

a=b×cos Δθ−b×sin Δθ tan ψ  (30)

Based on Equation (30), the angle ψ is acquired by using the followingEquation (31). Then, as represented in Equation (32), by subtractingthis angle ψ from the projection angle θ₂ for which the distance a ismeasured, the projection angle θ_(ref0) is calculated.

ψ=arctan(cot Δθ—(a/b)·csc Δθ)  (31)

θ_(ref0)=θ₂−ψ  (32)

Also for the ceiling 4, the distance measurement unit 1107 similarlymeasures distances c and d up to two arbitrary points. In addition, adifferential angle Δθ′ of projection directions in which the distances cand d are measured is acquired based on the projection angles θ₃ and θ₄for which the distances c and d are measured. Then, the distancemeasurement unit 1107 acquires a differential angle φ between theprojection angle θ₃ and the projection angle θ_(ref90) for which theprojection direction is perpendicular to the projection medium by usingthe distances c and d and the angle Δθ′ that have been acquired. Byadding the acquired angle φ and the projection angle θ₃, a projectionangle θ_(ref90) (another first direction) is calculated. A method ofcalculating the projection angle θ_(ref90) is similar to that describedusing Equations (27) to (32), and thus, the description thereof will notbe presented.

The distance measurement unit 1107 acquires a projection angle ωcorresponding to the boundary 5 between the wall 3 and the ceiling 4. Amethod of calculating the projection angle ω will be schematicallydescribed with reference to FIG. 54. As the coordinate system, in a casewhere a coordinate system in which the projection direction of aprojection angle θ=0° of the projector device 1 b is set as the X axis,and the projection direction of a projection angle θ=90° is set as the Yaxis is used, by acquiring coordinates (α, β) of an intersection betweena first line representing the wall 3 illustrated in FIG. 54 and a secondline representing the ceiling 4, the projection angle ω can becalculated by using the following Equations (33) and (34). In Equations(33) and (34), a value γ represents a distance from the origin (therotation center of the drum unit 10) of the coordinate system to thecoordinates (α, β).

γ²=α²+β²  (33)

ω=arccos(α/γ)  (34)

Here, the first line is acquired based on first coordinates of anintersection between the projection direction of the projection angleθ=0° and the first line and second coordinates of an intersectionbetween the projection direction of a projection angle θ_(ref0) that isperpendicular to the first line and the first line. In other words, thefirst and second coordinates are represented in the following Equations(35) and (36). In the following description, the projection angleθ_(ref0) is represented as an angle σ.

First Coordinates=(r ₀/cos σ,0)  (35)

Second Coordinates=(r ₀×cos σ,r ₀×sin σ)  (36)

The first line corresponds to a linear function, and the coordinates oftwo points passing through the first line are known. Thus, by applyingthe coordinates to a two-point standard type of a linear function, thefirst line is represented in the following Equation (37). Here, adistance r₀, for example, is acquired as r₀=a×cos θ₁ by referring toFIG. 53.

y=−x×cot σ+r ₀/sin σ  (37)

Similarly, the second line is acquired based on third coordinates of anintersection between the projection direction of the projection angleθ=90° and the second line and fourth coordinates of an intersectionbetween the projection direction of a projection angle θ_(ref90) that isperpendicular to the second line and the second line. In other words,the third and fourth coordinates are represented in the followingEquations (38) and (39). In the following description, the projectionangle θ_(ref90) is represented as an angle ε.

Third Coordinates=(0,r ₁/cos ε)  (38)

Fourth Coordinates=(r ₁×sin ε,r ₁×cos ε)  (39)

The second line corresponds to a linear function, and the coordinates oftwo points passing through the second line are known. Thus, by applyingthe coordinates to the two-point standard type of a linear function, thesecond line is represented in the following Equation (40). Here, adistance r₁, for example, is acquired as r₁=c×sin θ₃ by referring toFIG. 53.

y=−x×tan ε+r ₁/cos ε  (40)

Thus, based on Equations (37) and (40) described above, a value α and avalue β of the coordinates (α, β) of an intersection between the firstand second lines are acquired in the following Equations (41) and (42).By applying the values α and β acquired using Equations (41) and (42) toEquations (33) and (34) described above, the projection angle ω of theprojection direction corresponding to the boundary 5 is acquired.

α=−(r ₁×sin σ−r ₀×cos ε)/cos(σ+ε)  (41)

β={cos σ×(r ₁×sin σ−r ₀×cos ε)}/{sin σ cos(σ+ε)}+r ₀/sin σ  (42)

The distance measurement unit 1107 acquires distances up to theprojection medium for the projection direction that is perpendicular tothe projection medium acquired as above and selects a shortest distancer_(MIN) from among the acquired distances. In addition, the distancemeasurement unit 1107 acquires a projection angle θ_(MIN) correspondingto this shortest distance r_(MIN). The distance measurement unit 1107transmits the distance r_(MIN) and the projection angle θ_(MIN) acquiredas above to the image processor 1102.

Here, a method of changing the side that is used as the reference in thekeystone correction by using the projection angles θ_(ref0) andθ_(ref90) and the projection angle w, a method of designating the imagecut-out area, and the like are similar to those of the first distancemeasurement method described above, and the description thereof will notbe presented here.

Third Embodiment

Next, a third embodiment will be described. According to the projectordevices 1, 1 a, and 1 b described above, by emitting projection light tobe perpendicular to the projection face of the projection medium, anoptimal projection image can be acquired. Accordingly, generally, in aprojection device, an adjustment mechanism used for adjusting the angleof projection light is arranged. However, it is considered to bedifficult for a user to acquire an appropriate projection image bymanually adjusting the projection angle. For example, in order toacquire an appropriate projection image, the user needs to manuallyadjust the projection angle while visually checking the posture of theprojection device, the installation state of the projection medium, aprojection image projected from the projection device to the projectionmedium. In order to acquire an appropriate projection image by usingthis method, a lot of time is necessary, and the user is required tohave a corresponding technology. An object of the third embodiment is toprovide a projector device capable of easily acquiring an appropriateprojection image regardless of the posture of the projection device andthe like.

In addition, the functional configuration of the projector device 1 baccording to the second embodiment described with reference to FIG. 43may be applied to the third embodiment. The external appearance and theconfiguration of the projector device 1 b applied to the thirdembodiment are similar to those of the first embodiment.

However, as described above with reference to FIG. 38, the direction ofan increase in the distortion changes at predetermined projectiondirections (θ=−90°, 90°, and 0° and the boundaries 5 and 7 between thewall 3 and the ceiling 4 and the floor 6) as boundaries with respect toa monotonous increase in the projection angle θ. Among such projectiondirections, the projection angles θ=−90°, 90°, and 0° correspond toprojection directions that are perpendicular to the projection face ofthe projection medium, and, between before and after such projectiondirections, the direction of a change in the distance from theprojection lens 12 to the projection medium with respect to thedirection of the change in the projection angle θ changes. In addition,the boundaries 5 and 7 are portions at which the face of the projectionmedium is discontinuous, and, between before and after the projectiondirections, the direction of a change in the distance from theprojection lens 12 to the projection medium with respect to thedirection of the change in the projection angle θ changes.

Accordingly, between before and after the projection direction in whichthe direction of the change in the distance from the projection lens 12to the projection medium with respect to the direction of the change inthe projection angle θ, it is necessary to change a horizontalcorrection coefficient and a vertical correction coefficient accordingto the keystone correction according to the projection direction.Hereinafter, the horizontal correction coefficient and the verticalcorrection coefficient will be collectively referred to as correctioncoefficients.

In other words, as the correction coefficients, a first correctioncoefficient of which the degree (hereinafter, referred to as the degreeof distortion suppression) of suppression of horizontal and verticaldistortions of a projection image increases according to an increase inthe projection angle θ and a second correction coefficient of which thedegree of distortion suppression decreases according to an increase inthe projection angle θ are prepared in advance. The image processor 1102performs a keystone correction for image data to be projected byperforming switching between the first and second correctioncoefficients according to the projection angle θ.

In addition, as the first correction coefficient and the secondcorrection coefficient, the first correction coefficient k(θ, β) and thesecond correction coefficient k_(V)(d_(y)) acquired using Equations (10)to (19) in the first embodiment described above may be used.

More specifically, for example, as the rotation of the drum unit 10 isstarted from the projection angle θ=−90°, the image processor 1102selects the first correction coefficient between the projection angleθ=−90° and the boundary 7, and the second correction coefficient isselected between the boundary 7 and the projection angle θ=0°. Next, thefirst correction coefficient is selected between the projection angleθ=0° and the boundary 5, and the second correction coefficient isselected between the boundary 5 and the projection angle θ=90°. Inaddition, after the projection angle θ, until a next boundary betweenthe ceiling and the wall, the first correction coefficient is selected.

In a case where the first and second correction coefficients areselected according to the projection angle θ as described above, theprojection directions for the projection angles θ=−90°, 0°, and 90° inthe projector device 1 b need to be perpendicular to the floor 6, thewall 3, and the ceiling 4 that are projection media. On the other hand,in a case where the projector device 1 b is disposed to be inclined withrespect to the rotation direction of the drum unit 10, such projectiondirections are not perpendicular to the floor 6, the wall 3, and theceiling 4. In such a case, when the projection angle θ of the projectordevice 1 b is used as a parameter of the projection angle θ included inthe first and second correction coefficients, a correction other thanthe correction to be performed for the actual projection direction isperformed.

In the third embodiment, a projection angle θ (=the projection angleθ_(ref)) for which the projection direction of the projection lens 12 isperpendicular to the projection medium is acquired based on a distancefrom the projector device 1 b to the projection medium that is measuredusing the distance sensor 60. In addition, based on the distance, aprojection angle of an intersection of two projection media intersectingwith each other such as the wall 3 and the ceiling 4, in other words, aprojection angle for the boundary 5 between the wall 3 and the ceiling 4is acquired. The image processor 1102, between before and after theacquired projection angle of the boundary 5, performs a keystonecorrection by performing switching between the first and secondcorrection coefficients.

More specifically, the projector device 1 b according to the thirdembodiment acquires the projection angle θ_(M) of the boundary 5 byusing the first distance measurement method that is common to the secondembodiment and the modified example of the second embodiment describedabove and performs the keystone correction by performing switchingbetween the first and second correction coefficients between before andafter the projection angle θ_(M). Alternatively, the projector device 1b according to the third embodiment acquires the projection angle ω ofthe boundary 5 by using the first distance measurement method that iscommon to the second embodiment and the modified example of the secondembodiment described above and performs the keystone correction byperforming switching between the first and second correctioncoefficients between before and after the projection angle ω.

Flow of Process of Performing Projection of Image Data

Next, the flow of the image projecting process performed by theprojector device 1 b according to the third embodiment will be describedwith reference to a flowchart illustrated in FIG. 55.

First, in Step S700, the distance measurement unit 1107 acquires aprojection angle θ_(ref) or a projection angle θ_(ref0) for which theprojection direction is perpendicular to the projection medium as areference angle used at the time of performing the projection process byusing the first distance measurement method or the second distancemeasurement method described above. In addition, at this time, thedistance measurement unit 1107 also acquires a projection angle θ_(M) ora projection angle ω of a projection direction corresponding to theboundary of the projection medium. The operation of Step S700, forexample, is performed as an initial operation of the projector device 1b. Hereinafter, the reference angle and the like will be described asbeing acquired by using the first distance measurement method.

In the next Step S701, in accordance with the input of image data,various set values relating to the projection of an image according tothe image data are input to the projector device 1 b. The input variousset values, for example, are acquired by the CPU 1120. The various setvalues acquired here, for example, include a value representing whetheror not the image according to the image data is rotated, in other words,whether or not the horizontal direction and the vertical direction ofthe image are interchanged, an enlargement rate of the image, and anoffset angle θ_(ofst) at the time of projection. The various set valuesmay be input to the projector device 1 b as data in accordance with theinput of the image data to the projector device 1 b or may be input byoperating the operation unit 14.

In the next Step S702, image data corresponding to one frame is input tothe projector device 1 b, and the input image data is acquired by theimage cutting-out unit 1100. The acquired image data is written into theimage memory 101.

In the next Step S703, the image control unit 1103 acquires the offsetangle θ_(ofst). In the next Step S704, the image control unit 1103acquires the cut out size, in other words, the size of the cut-out areaof the input image data. The image control unit 1103 may acquire thesize of the cut-out area from the set value acquired in Step S701 or maybe acquired according to an operation for the operation unit 14. In thenext Step S705, the image control unit 1103 acquires the view angle α ofthe projection lens 12. The image control unit 1103 acquires the viewangle α of the projection lens 12, for example, from the view anglecontrol unit 106.

In addition, in the next Step S706, the distance measurement unit 1107acquires the projection angle θ of the projection lens 12, for example,from the rotation control unit 104. The distance measurement unit 1107corrects the acquired projection angle θ by using the projection angleθ_(ref) that is the reference angle acquired in Step S700, therebyacquiring a projection angle θ′. This projection angle θ′ is transmittedto the image processor 1102 and the image control unit 1103.

In the next Step S707, the image control unit 1103 acquires a cut-outarea of the input image data by using Equations (3) to (8) describedabove based on the offset angle θ_(ofst), the size of the cut-out area,the view angle α, and the projection angle θ′ corrected by the distancemeasurement unit 1107 that are acquired in Steps S703 to S706. The imagecontrol unit 1103 instructs the image cutting-out unit 1100 to readimage data from the acquired cut-out area. The image cutting-out unit1100 reads image data within the cut-out area from the image data storedin the image memory 101 according to an instruction transmitted from theimage control unit 1103, thereby performing cutting out of the imagedata. The image cutting-out unit 1100 supplies the image data of thecut-out area read from the image memory 101 to the image processor 1102.

In Step S708, the image processor 1102 performs a size convertingprocess, for example, by using Equations (1) and (2) described above forthe image data supplied from the image cutting-out unit 1100. Inaddition, the image processor 1102 performs a keystone correctionaccording to the projection angle θ′ corrected by the distancemeasurement unit 1107 for the image data. At this time, the imageprocessor 1102 selects a correction coefficient based on informationrepresenting one of the first and second correction coefficients to beused, which is supplied from the distance measurement unit 1107, andperforms a keystone correction.

The image data for which the size converting process and the keystonecorrection have been performed by the image processor 1102 is suppliedto the display element 114. The display element 114 modulates lightsupplied from the light source 111 based on the image data and emits themodulated light. The emitted light is projected from the projection lens12.

In the next Step S709, the CPU 1120 determines whether or not there isan input of image data of the next frame of the image data input in StepS702 described above. In a case where it is determined that there is aninput of the image data of the next frame, the CPU 1120 returns theprocess to Step S702 and performs the processes of Steps S702 to S708described above for the image data of the next frame. In other words,the processes of Steps S702 to S708, for example, is repeated in unitsof frames of the image data according to the vertical synchronizationsignal VD of the image data. Thus, the projector device 1 b can causeeach process to follow a change in the projection angle θ in units offrames.

On the other hand, in Step S709, in a case where it is determined thatthe image data of the next frame has not been input, the CPU 1120 stopsthe image projecting operation of the projector device 1 b. For example,the CPU 1120 performs control of the light source 111 to be in the Offstate and instructs a rotation mechanism unit 105 to return the postureof the drum unit 10 to the initial posture. Then, after the posture ofthe drum unit 10 is returned to the initial posture, the CPU 1120 stopsa fan that cools the light source 111 and the like.

As above, according to the projector device 1 b, while the resolution ofthe image data is maintained, the user can perform image projection inwhich the position of a projected subject image can be easily checked inan image relating to the input image data.

Fourth Embodiment

Next, a fourth embodiment will be described. The output of anoptical-type distance sensor (the distance sensor 60) disposed in thewindow portion 13 is not necessarily stable but minutely changesconstantly due to the influence of an external disturbance,environments, or the like. Accordingly, also when the distance betweenthe projection device and a projection medium is fixed, an in-focusdistance according to automatic focusing minutely changes continuouslyby being reflected according to the change of the output of the distancemeasurement sensor. Such a minute change of the automatic focusing isnot of a degree causing the external appearance of a projection imageprojected onto the projection medium to be discomfort.

Meanwhile, according to the continuous minute change of the automaticfocusing, a focusing lens system included in a projection optical systemis continued to be driven minutely, and wear or fatigue of a mechanicalpart such as a gear that drives the lens system is promoted. Thisbecomes a factor that degrades the reliability of the device. Incontrast to this, it may be considered to increase a margin of theoutput of the distance sensor so as to cause the minute change of theoutput of the distance sensor to be ignorable. However, in such a case,it is difficult to appropriately perform in-focusing according toautomatic focusing, and there is concern that the external appearance ofa projection image projected onto the projection medium becomesdiscomfortable. An object of the fourth embodiment is to appropriatelycontrol the automatic focusing performed in the projector device.

Internal Configuration of Projector Device According to FourthEmbodiment

FIG. 56 is a block diagram that illustrates an example of the functionalconfiguration of a projector device 1 c according to a fourthembodiment. In FIG. 56, the same reference numeral is assigned to aportion common to the configuration illustrated in FIGS. 4 and 43described above, and detailed description thereof will not be presented.The external appearance and the structure of the projector device 1 caccording to the fourth embodiment are similar to those of the firstembodiment.

As illustrated in FIG. 56, the drive system control unit 91 illustratedin FIG. 4 includes: a lens control unit 511; a rotation control unit512; and a rotation mechanism unit 105. In the example illustrated inFIG. 56, while the output of an operation unit 14 is represented to bedirectly input to the lens control unit 511 and the rotation controlunit 512, actually, the output of the operation unit 14 is supplied toan overall control unit 120, and the overall control unit 120 controlsthe lens control unit 511 and the rotation control unit 512 according toa user's operation for the operation unit 14.

As illustrated in FIG. 56, a distance value output unit 510 is arranged,and a detection signal output from the distance sensor 60 is supplied tothe distance value output unit 510. The distance value output unit 510outputs a distance value 562 representing a distance from the projectionlens 12 to the projection medium based on the detection signal suppliedfrom the distance sensor 60.

As illustrated in FIG. 56, an optical engine unit 110 includes: a lightsource 111; a display element 500; an emission optical system 501; and adisplay element driving circuit 502. The display element 500 configured,for example, by a transmission-type liquid crystal display device isdriven by a display element driving circuit 502, modulates light of eachof colors RGB based on image data, transmits the modulated light, andemits the light. In other words, the display element 500 and the displayelement driving circuit 502 correspond to the display element 114illustrated in FIG. 4 and the like. The light 520 of the colors RGB,which is modulated based on the image data, emitted from the displayelement 500 is incident to the emission optical system 501 and isprojected to the outside of the projector device 1 c from the projectionlens 12 included in the emission optical system 501.

FIG. 57 is a block diagram that illustrates the configuration of anexample of the emission optical system 501. The emission optical system501 includes: the projection lens 12; a focus adjusting unit 5010; and alens driving unit 5011. The focus adjusting unit 5010, for example,includes a plurality of combined lenses and adjusts the focus of lightpassing through it according to the driving of the lens driving unit5011. The lens driving unit 5011, for example, drives some of theplurality of lenses included in the focus adjusting unit 5010 based onan in-focus control signal 561 and adjusts the focus of light passingthrough the focus adjusting unit 5010 for the projection medium. Inaddition, the lens driving unit 5011 outputs lens position information560 that represents the position of a lens driven for adjusting thefocus.

As described above, the optical engine unit 110 is disposed inside thedrum unit 10 that can be rotated by the rotation mechanism unit 105. Therotation mechanism unit 105 includes the drive unit 32 described withreference to FIGS. 2A and 2B and a gear 35 that is a configuration ofthe drum unit 10 side and rotates the drum unit 10 by a predeterminedamount by using the rotation of the motor. In other words, theprojection direction of the projection lens 12 is changed by therotation mechanism unit 105.

The image data 550 of a still image or a moving image is input to theprojector device 1 c and is supplied to the image processing/controllingunit 90. The image processing/controlling unit 90 performs imageprocessing for the supplied image data as is necessary, stores theprocessed image data in a memory not illustrated in the figure, cuts outimage data of an image area according to angle information, which issupplied from the rotation control unit 512, from the image data storedin the memory, performs image processing for the cut-out image data asis necessary, and outputs the processed cut-out image data. The imagedata output from the image processing/controlling unit 90 is supplied tothe display element driving circuit 502, and the display element drivingcircuit 502 drives the display element 500 based on the image data.

The rotation control unit 512 instructs the rotation mechanism unit 105,for example, in accordance with a user's operation for the operationunit 14. In addition, the rotation mechanism unit 105 includes photointerrupters 51 a and 51 b. The rotation mechanism unit 105 controls thedrive unit 32 in accordance with the instruction supplied from therotation control unit 512 and controls the rotation operation of thedrum unit 10 (the drum 30). For example, the rotation mechanism unit 105generates a drive pulse in accordance with the instruction supplied fromthe rotation control unit 512, thereby driving the motor. The rotationcontrol unit 512 generates an operation flag representing whether or notthe drum unit 10 is in the middle of the rotation operation based on thedrive pulse generated by the rotation mechanism unit 105.

Meanwhile, the outputs of the photo interrupters 51 a and 51 b and thedrive pulse used for driving the motor are supplied from the rotationmechanism unit 105 to the rotation control unit 512. The rotationcontrol unit 512, for example, counts the number of drive pulses using acounter, acquires detection timing of the protrusion 46 a based on theoutput of the photo interrupter 51 b, and resets the counted number ofpulses at the detection timing of the protrusion 46 a. The rotationcontrol unit 512 sequentially acquires the angle of the drum unit 10(the drum 30) based on the counted number of pulses. The angleinformation representing the angle of the drum unit 10 is supplied tothe image processing/controlling unit 90.

A detection signal output from the distance sensor 60 is input to thedistance value output unit 510. The distance value output unit 510performs a distance measuring process based on the detection signal andderives a distance between the projection lens 12 and the projectionmedium. The distance value output unit 510 supplies a distance value 562representing the derived distance to the lens control unit 511.

The lens control unit 511 generates an in-focus control signal 561 usedfor controlling the focus adjusting unit 5010 included in the emissionoptical system 501 by using the distance value 562 supplied from thedistance value output unit 510 as a first distance value. In addition,the lens control unit 511 controls the generation of the in-focuscontrol signal 561 by using the distance value supplied from thedistance value output unit 510 as a second distance value.

The overall control unit 120 can exchange commands and data among theimage processing/controlling unit 90, the distance value output unit510, the lens control unit 511, the rotation control unit 512, and theoperation unit 14 through a path not illustrated in the figure.

FIG. 58 illustrates the configuration of an example of the lens controlunit 511. The lens control unit 511 includes: a determination unit 5110;a register 5111; an in-focus control signal generating unit 5112; and atimer 5113. The timer 5113 measures time under the control of thedetermination unit 5110.

To the lens control unit 511, the distance value 562 is input from thedistance value output unit 510, and the lens position information 560representing the current lens position D_(L) is input from the lensdriving unit 5011. The distance value 562 input to the lens control unit511 is supplied to the in-focus control signal generating unit 5112through the register 5111. The in-focus control signal generating unit5112 uses the supplied distance value 562 for the process as the firstdistance value. In addition, the distance value 562 input to the lenscontrol unit 511 is supplied to the determination unit 5110. Thedetermination unit 5110 uses the supplied distance value 562 for theprocess as the second distance value. The lens position information 560input to the lens control unit 511 is supplied to the determination unit5110 and the in-focus control signal generating unit 5112. In addition,the operation flag representing whether or not the drum unit 10 is inthe middle of the rotation operation is supplied to the determinationunit 5110 from the rotation control unit 512.

The lens control unit 511 generates the in-focus control signal 561 usedfor controlling the focus adjusting unit 5010 included in the emissionoptical system 501 by using the distance value 562 supplied from thedistance value output unit 510 as the first distance value. In addition,the lens control unit 511 controls the generation of the in-focuscontrol signal 561 by using the distance value 562 supplied from thedistance value output unit 510 as the second distance value.

The in-focus control signal generating unit 5112 generates the in-focuscontrol signal 561 based on the lens position information 560 and thefirst distance value read from the register 5111. Here, the control ofthe focus adjustment performed by the focus adjusting unit 5010 will beschematically described with reference to FIG. 59. Here, the focus willbe described to be adjusted by moving the lens 5130 forward or backwardwith respect to the projection direction among the plurality of lensesincluded in the focus adjusting unit 5010. The adjustment of the focusmay be performed by moving a plurality of lenses including the lens 5130with respect to the projection direction.

In FIG. 59, the horizontal axis represents a position along theprojection direction of the lens 5130. A target position D₀ of the lens5130 is set based on the distance value 562 output from the distancevalue output unit 510. This target position D₀ is a position at which animage projected from the projection lens 12 is in focus with theprojection medium in a case where the lens 5130 is located at theposition.

In a case where the current lens position D_(L) of the lens 5130 isdifferent from the target position D₀, a deviation ΔD of the currentlens position D_(L) from the target position D₀ occurs. The deviation ΔDis a value that represents a deviation on the projection medium from thein-focus state of an image projected from the projection lens 12. Inother words, as the absolute value of the deviation ΔD decreases, a morein-focus state is formed. On the other hand, as the absolute value ofthe deviation ΔD increases, the state deviates more from the in-focusstate. In order to cause the projection image to be in focus for theprojection medium, the lens control unit 511 moves the position of thelens 5130 such that the deviation ΔD becomes zero.

More specifically, in the lens control unit 511, the in-focus controlsignal generating unit 5112 sets a first target position D₀ _(—) ₁according to the first distance value read from the register 5111. Inaddition, the in-focus control signal generating unit 5112 acquires thelens position information 560 representing the current lens positionD_(L) of the lens 5130 of the focus adjusting unit 5010 from the lensdriving unit 5011.

The in-focus control signal generating unit 5112 calculates a firstdeviation ΔD₁ based on the set first target position D₀ _(—) ₁ and thecurrent lens position D_(L) represented in the acquired lens positioninformation 560. Then, the in-focus control signal generating unit 5112generates a drive control signal for moving the lens 5130 by thedeviation ΔD and outputs the generated drive control signal as thein-focus control signal 561. The in-focus control signal 561 is input tothe emission optical system 501 and is supplied to the lens driving unit5011. The lens driving unit 5011 drives the focus adjusting unit 5010based on the supplied in-focus control signal 561.

As above, the in-focus control signal generating unit 5112 and the lensdriving unit 5011 configure a focus adjusting/driving unit that drivesthe focus adjusting unit 5010 in cooperation with each other.

The determination unit 5110 sets a second target position D₀ _(—) ₂based on the second distance value. The determination unit 5110calculates a second deviation ΔD₂ based on the second target position D₀_(—) ₂ and the current lens position D_(L). In addition, a first valueth₁ set as a threshold th and a second value th₂ that is larger than thefirst value th₁ are input to the determination unit 5110. For example,the first value th₁ and the second value th₂ are input from the overallcontrol unit 120. However, the first value th₁ and the second value th₂are not limited thereto but may be stored in a register not illustratedin the figure or the like in advance. In addition, the determinationunit 5110 determines whether or not update of the register 5111 isperformed based on the second deviation ΔD₂ acquired based on the secondtarget position D₀ _(—) ₂ and the current lens position D_(L), theoperation flag, and the threshold th to which the first value th₁ or thesecond value th₂ is set. Then, the determination unit 5110 generates aregister control signal used for controlling the update of the register5111 based on a result of the determination. In other words, thedetermination unit 5110 serves as a control unit controlling whether ornot the update of the register 5111 is performed. The determinationprocess performed by the determination unit 5110 will be describedlater.

Here, while the image processing/controlling unit 90, the distance valueoutput unit 510, the lens control unit 511, and the rotation controlunit 512 have been described to be configured as separated hardware, theembodiment is not limited thereto. For example, all or some of the imageprocessing/controlling unit 90, the distance value output unit 510, thelens control unit 511, and the rotation control unit 512 may be realizedby a module of a program operating on the CPU as the function of theoverall control unit 120.

Focus Adjusting Process According to Embodiment

Next, a focus adjusting process according to a fourth embodiment will bedescribed. As described with reference to FIG. 59, in a case where theposition of the lens 5130 is controlled such that the deviation ΔDbecomes zero, the absolute value of the deviation ΔD is controlled so asto be the threshold th set in advance or less. In the fourth embodiment,a first value th₁ and a second value th₂ that is larger than the firstvalue th₁ are prepared, and one of the first value th₁ and second valueth₂ is set as the threshold th for the absolute value of the deviationΔD depending on the condition.

FIG. 60 is a flowchart that illustrates an example of a method ofcontrolling the register 5111 that is executed by the determination unit5110. Before the execution of the process of the flowchart representedin FIG. 60, the determination unit 5110 sets the first value th₁ as aninitial value of the threshold th. In addition, the determination unit5110 illustrated in FIG. 58 resets an elapsed time measured by the timer5113 to zero.

In Step S800, the determination unit 5110 determines whether the currentthreshold th for the absolute value of the second deviation ΔD₂ is thefirst value th₁ or the second value th₂. In a case where the currentthreshold th is determined to be the first value th₁, the determinationunit 5110 causes the process to proceed to Step S801 and determineswhether or not the absolute value of the second deviation ΔD₂ is lessthan the first value th₁. In a case where the absolute value of thesecond deviation ΔD₂ is determined to be the first value th₁ or more,the determination unit 5110 causes the process to proceed to Step S806,resets the elapsed time measured by the timer 5113 to zero, and returnsthe process to Step S800.

In a case where the absolute value of the second deviation ΔD₂ isdetermined to be less than the first value th₁ in Step S801, thedetermination unit 5110 causes the process to proceeds to Step S802 andupdates the elapsed time. Then, the determination unit 5110 determineswhether or not the elapsed time exceeds the time set in advance in thenext Step S803. In a case where the elapse time is determined not toexceed the time, the determination unit 5110 returns the process to StepS800.

On the other hand, in a case where the elapsed time is determined toexceed the time set in advance in Step S803, the determination unit 5110causes the process to proceed to Step S804 and sets the second value th₂as the current threshold th. Then, in the next Step S805, thedetermination unit 5110 generates a register control signal used forstopping the update of the register 5111 and supplies the generatedregister control signal to the register 5111. In accordance with thisregister control signal, the update of the content stored in theregister 5111 is stopped, and the distance value (first distance value)used by the in-focus control signal generating unit 5112 for calculatingthe first deviation ΔD₁ is fixed to the distance value 562 that isoutput from the distance value output unit 510 immediately before thestopping of the update of the register 5111. Then, the process isreturned to Step S800.

In other words, in Step S803, in a case where the absolute value of thesecond deviation ΔD₂ is maintained to be in the state of being less thanthe first value th₁, and the elapsed time exceeds the time set inadvance, the position of the focus can be regarded not to change for atime determined in advance. In such a case, it can be supposed that therelation between the projection lens 12 and the projection medium isfixed. Thus, by fixing the first distance value used by the in-focuscontrol signal generating unit 5112 for generating the in-focus controlsignal 561, the influence of swinging of the detection signal outputfrom the distance sensor 60 on the focus adjustment can be removed, anda continuous minute change in the focus adjusting unit 5010 issuppressed.

In addition, in the process until Step S804, the second deviation ΔD₂calculated by the determination unit 5110 based on the second distancevalue and the current lens position D_(L) and the first deviation ΔD₁calculated by the in-focus control signal generating unit 5112 based onthe first distance value and the current lens position D_(L) use thedistance value 562 supplied from the distance value output unit 510 andhave the same value. In Step S805, when the update of the distance value562 in the register 5111 is stopped, the in-focus control signalgenerating unit 5112 calculates the first deviation ΔD₁ based on thedistance value 562 supplied before the stop of the update of theregister 5111. In such a case, since the distance value 562 supplied tothe in-focus control signal generating unit 5112 is not changed but canbe regarded as a fixed value, the first deviation ΔD₁ does not change aswell. On the other hand, the determination unit 5110 calculates thesecond deviation ΔD₂ according to a change in the distance value 562directly supplied from the distance value output unit 510. For thatreason, the second deviation ΔD₂ changes also after Step S805.

In Step S800, when the current threshold th is determined to be thesecond value th₂, the determination unit 5110 causes the process toproceed to Step S810. In Step S810, the determination unit 5110determines whether or not the operation flag representing whether or notthe drum unit 10 is in the middle of the rotation operation is On, inother words, whether or not the drum unit 10 is in the middle of therotation operation. The determination unit 5110, for example, canacquire the operation flag based on the drive pulse of the motor that issupplied from the rotation mechanism unit 105 to the rotation controlunit 512.

In Step S810, in a case where it is determined that the operation flagis Off, in other words, the drum unit 10 is not in the middle of therotation operation, the determination unit 5110 returns the process toStep S800.

On the other hand, in a case where the operation flag is determined tobe On in Step S810, the determination unit 5110 causes the process toproceed to Step S811 and determines whether or not the absolute value ofthe second deviation ΔD₂ is less than the second value th₂. In a casewhere the absolute value of the second deviation ΔD₂ is determined to beless than the second value th₂, the determination unit 5110 returns theprocess to Step S800.

In Step S811, in a case where the absolute value of the second deviationΔD₂ is determined to be the second value th₂ or more, the determinationunit 5110 causes the process to Step S812 and resets the elapsed timethat is measured by the timer 5113 to zero.

Then, in the next Step S813, the determination unit 5110 sets the firstvalue th₁ as the current threshold th and causes the process to proceedto Step S814. In Step S814, the determination unit 5110 generates aregister control signal restarting the update of the register 5111 andsupplies the generated register control signal to the register 5111.Accordingly, the fixing of the first distance value used by the in-focuscontrol signal generating unit 5112 for calculating the first deviationΔD₁, which is performed in Step S805 described above, is released. Inother words, the distance value 562 supplied from the distance valueoutput unit 510 to the register 5111 is supplied to the in-focus controlsignal generating unit 5112 again and is used as the first distancevalue for the calculation of the first deviation ΔD₁. Accordingly, thefirst deviation ΔD₁ calculated by the in-focus control signal generatingunit 5112 is updated in accordance with the distance value 562 outputfrom the distance value output unit 510. When the determination unit5110 restarts the update of the register 5111 and releases the fixing ofthe second distance value stored in the register 5111, the process isreturned to Step S800. Accordingly, the focus adjustment at the firstvalue th₁, which is performed in Step S801 and the subsequent steps, isrestarted.

After Step S810, the process starting from Step S811 relates to thefocus adjusting process in the middle of the rotation of the drum unit10. In the middle of the rotation of the drum unit 10, the projectiondirection according to the projection lens 12 changes in accordance withthe rotation of the drum unit 10, and a distance between the projectionlens 12 and the projection medium changes in accordance with the change,and accordingly, it is necessary to constantly monitor the focus.Accordingly, in Step S811, at a time point at which the absolute valueof the second deviation ΔD₂ becomes the second value th₂ or more, thethreshold th for the absolute value of the second deviation ΔD₂ ischanged to the first value th₁ of the initial value, and the fixing ofthe distance value 562 supplied to the in-focus control signalgenerating unit 5112 is released, and ordinary focus adjustment isperformed.

On the other hand, in a case where the rotation of the drum unit 10 isminute, and the absolute value of the second deviation ΔD₂ is less thanthe second value th₂, the first distance value used by the in-focuscontrol signal generating unit 5112 is maintained to be fixed.Accordingly, there is no change in the first deviation ΔD₁ calculated bythe in-focus control signal generating unit 5112, and unnecessarymovement of the focus adjusting unit 5010 is suppressed.

Another Example of Register Control Method Executed by DeterminationUnit

Next, another example of the method of controlling the register 5111that is executed by the determination unit 5110 according to the fourthembodiment will be described. In this another example, theconfigurations described with reference to FIGS. 1A and 1B, FIGS. 2A and2B, FIG. 3, and FIGS. 56 to 59 can be directly applied, and thus,detailed description thereof will not be presented here. FIG. 61 is aflowchart that illustrates another example of the method of controllingthe register 5111 that is executed by the determination unit 5110.

In Step S900, the determination unit 5110 determines whether or not theoperation flag representing whether or not the drum unit 10 is in themiddle of the rotation operation is On, in other words, whether or notthe drum unit 10 is in the middle of the rotation operation. In a casewhere the operation flag is determined to be On in Step S900, thedetermination unit 5110 causes the process to proceed to Step S901 anddetermines whether or not the absolute value of the second deviation ΔD₂is less than the first value th₁. In a case where the absolute value ofthe second deviation ΔD₂ is determined to be less than the first valueth₁, the determination unit 5110 causes the process to proceed to StepS903.

In Step S903, the determination unit 5110 generates a register controlsignal used for stopping the update of the register 5111 and suppliesthe generated register control signal to the register 5111. Inaccordance with this register control signal, the update of the contentstored in the register 5111 is stopped, and the first distance valueused by the in-focus control signal generating unit 5112 for calculatingthe first deviation ΔD₁ is fixed to the distance value 562 that isoutput from the distance value output unit 510 immediately before thestop of the update of the register 5111. Then, the process is returnedto Step S900.

In addition, in Step S903, in a case where the update of the register5111 is stopped, the state is maintained, and the content stored in theregister 5111 is maintained as it is.

In Step S901, in a case where the absolute value of the second deviationΔD₂ is determined to be the first value th₁ or more, the determinationunit 5110 causes the process to proceed to Step S902. The determinationunit 5110, in Step S902, generates a register control signal restartingthe update of the register 5111 and supplies the generated registercontrol signal to the register 5111. Accordingly, the fixing of thefirst distance value used by the in-focus control signal generating unit5112 for calculating the first deviation ΔD₁, which is performed in StepS903 described above, is released. Then, the process is returned to StepS900.

On the other hand, in a case where the operation flag is determined tobe Off in Step S900 described above, the determination unit 5110 causesthe process to proceed to Step S904. The determination unit 5110determines whether or not the absolute value of the second deviation ΔD₂is less than the second value th₂ in Step S904. In a case where theabsolute value of the second deviation ΔD₂ is determined to be thesecond value th₂ or more, the determination unit 5110 causes the processto proceed to Step S902 described above, and the fixing of the firstdistance value is released.

On the other hand, in a case where the absolute value of the seconddeviation ΔD₂ is determined to be less than the second value th₂ in StepS904, the determination unit 5110 causes the process to Step S903described above and fixes the first distance value. Then, the process isreturned to Step S900.

As above, also in this another example, similar to the example describedwith reference to FIG. 60, also in the middle of the rotation of thedrum unit 10, in a case where the rotation of the drum unit 10 isminute, and the absolute value of the second deviation ΔD₂ is fittedinto the first value th₁, the first distance value used by the in-focuscontrol signal generating unit 5112 is maintained to be fixed.Accordingly, there is no change in the first deviation ΔD₁ calculated bythe in-focus control signal generating unit 5112, and unnecessarymovement of the focus adjusting unit 5010 is suppressed. In addition,according to the flowchart represented in FIG. 61, the control processcan be realized with the number of steps less than that of the flowchartrepresented in FIG. 60.

As above, according to the fourth embodiment, the focus adjusting unit5010 is appropriately controlled according to a change in the distancebetween the projection lens 12 and the projection medium and with orwithout rotation of the drum unit 10 and the magnitude thereof.Accordingly, wear or fatigue of the mechanical portion of the focusadjusting unit 5010 is suppressed, and a situation in which the externalappearance of a projection image projected onto the projection medium isdiscomfort can be prevented.

Modified Example of Fourth Embodiment

In the description presented above, while the value representing adeviation of the image, which is projected from the projection lens 12,from the in-focus state on the projection medium is acquired based onthe distance between the projection lens 12 and the projection medium,the method of acquiring the value is not limited thereto. Thus, thevalue representing a deviation from the in-focusing may be acquired byusing another method. For example, the degree of in-focusing may beacquired based on an image projected onto the projection medium. In sucha case, the distance sensor 60 is replaced with an imaging device suchas a charge coupled device (CCD), a complementary metal oxidesemiconductor (CMOS), or an imager, and the distance value output unit510 is replaced with an analysis unit. Based on a result of the analysisof a captured image that is performed by the analysis unit, the lenscontrol unit 511 acquires the value representing a deviation from thein-focus state. For example, the lens control unit 511 may use a methodof acquiring a deviation from the in-focus state based on the contrastof an image or a method of acquiring a deviation from the in-focus statebased on a phase difference of light that is divided into two parts andis incident to the imaging device.

In addition, two or more of the first to fourth embodiments describedabove may be combined together.

According to the present invention, a projection device, an imagecorrection method, and a program capable of effectively using a pixelarea displayable in a display device can be provided.

Although the invention has been described with respect to specificembodiments for a complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art that fairly fall within the basic teaching herein setforth.

What is claimed is:
 1. A projection device comprising: a projection unitincluding a display element in which a plurality of pixel lines eachformed by a plurality of pixels arranged in a first direction arearranged in a second direction perpendicular to the first direction andan optical system that projects light emitted from the display elementand projecting an image based on input image data; a first correctionunit configured to correct a scale of each line data of the image datathat corresponds to each of the pixel lines based on a position of theeach of the pixel lines in the second direction in the display elementand a second-direction component of inclination of a projectiondirection of the projection unit with respect to a normal line of aprojection face onto which the image is projected; a second correctionunit configured to correct a second-direction scale of each pixel dataof the image data after the correction performed by the first correctionunit based on a position of each pixel in the second direction in thedisplay element and the second-direction component of the inclination ofthe projection direction of the projection unit with respect to thenormal line of the projection face onto which the image is projected;and an image cutting-out unit configured to cut-out image data of anarea, which is projected from the projection unit, of the image dataafter the correction performed by the second correction unit and inputthe image data of the area to the projection unit.
 2. The projectiondevice according to claim 1, further comprising: a first correctioncontrol unit configured to calculate a first correction coefficient usedfor correcting the scale of each line data of the image data thatcorresponds to each of the pixel lines based on a position of the eachof the pixel lines in the second direction in the display element andthe second-direction component of the inclination of the projectiondirection of the projection unit with respect to the normal line of theprojection face onto which the image is projected; and a secondcorrection control unit configured to calculate a second correctioncoefficient used for correcting the scale of each pixel data in thesecond direction in the image data after the correction performed by thefirst correction unit based on a position of the each pixel in thesecond direction in the display element and the second-directioncomponent of the inclination of the projection direction of theprojection unit with respect to the normal line of the projection faceonto which the image is projected, wherein the first correction unit isconfigured to correct the scale of each line data of the image data thatcorresponds to each of the pixel lines by using the first correctioncoefficient calculated by the first correction unit, and wherein thesecond correction unit corrects the scale of each pixel data in thesecond direction by using the second correction coefficient calculatedby the second correction control unit.
 3. The projection deviceaccording to claim 2, wherein the second correction control unit isconfigured to convert the position of each pixel in the second directioninto an angle having a center axis of the projection unit in theprojection direction as a reference and calculate the second correctioncoefficient corresponding to each pixel in accordance with the angleafter the conversion.
 4. The projection device according to claim 2,wherein the second correction control unit is configured to calculatethe second correction coefficients for at least two pixels among theplurality of pixels, which are arranged in the second direction, of theimage data after the correction performed by the first correction unitand calculate the second correction coefficient for another pixel amongthe plurality of pixels arranged in the second direction by performinglinear interpolation of the second correction coefficients calculatedfor the at least two pixels.
 5. The projection device according to claim1, further comprising: a distance value output unit configured to outputa distance value representing a measured distance from the projectionunit to the projection medium; a focus adjusting unit configured toadjust focus of light passing through the projection unit; a focusadjusting/driving unit configured to detect a first deviation from anin-focus state of the light projected onto the projection medium by theprojection unit based on a first distance value by using the distancevalue as the first distance value and drive the focus adjusting unitsuch that a value representing the first deviation becomes zero; adetermination unit configured to detect a second deviation from thein-focus state of the light based on a second distance value by usingthe distance value as the second distance value and determine whether ornot a value representing the second deviation is less than a threshold;and a focus adjusting/controlling unit configured to set the thresholdof the determination unit to a second value larger than a first valueand stop updating the first distance value of the focusadjusting/driving unit in a case where the determination unit determinesthat the threshold is the first value, and a state in which the valuerepresenting the second deviation is less than the first value iscontinued for a time set in advance.
 6. The projection device accordingto claim 5, wherein the focus adjusting/controlling unit is configuredto set the threshold value to the first value and restart updating ofthe first distance value in a case where the determination unitdetermines that the threshold is the second value, the projectiondirection of the projection unit is in the middle of being changed, andthe value representing the second deviation is the threshold or more. 7.A projection device comprising: a projection direction changing unitconfigured to change a projection direction of a projection unit thatconverts image data into light and projects the light; a projectiondirection acquiring unit configured to measure a distance up to aprojection medium onto which the projection unit projects light andacquire a first projection direction in which the distance is theshortest; a ratio acquiring unit configured to acquire a ratio of a sizeof each projection image on the projection medium that is acquired byprojecting an image according to the image data in each secondprojection direction using the projection unit to a size of a projectionimage on the projection medium that is projected in the first projectiondirection; and an image processor configured to perform a reductionprocess according to the ratio acquired by the ratio acquiring unit forthe image data projected by the projection unit.
 8. The projectiondevice according to claim 7, wherein the ratio acquiring unit isconfigured to acquire the ratio based on the second projectiondirection, a distance up to the projection medium in the firstprojection direction, and a view angle according to the projection unit.9. The projection device according to claim 7, wherein the imageprocessor performs the reduction process for the image data and performsa trapezoidal distortion correction for the image data for which thereduction process is performed along the projection direction.
 10. Theprojection device according to claim 7, wherein the projection directionacquiring unit is configured to detect first inflection points ofdownward projections in a change in the measured distance while changingthe projection direction of the projection unit by using the projectiondirection changing unit and acquire a projection direction correspondingto the first inflection point, for which the distance is the shortest,among the detected first inflection points as the first projectiondirection.
 11. The projection device according to claim 7, wherein theprojection direction acquiring unit is configured to measure distancesin two projection directions for each face of the projection medium forwhich the projection unit can perform projection, acquire thirdprojection directions perpendicular to the projection medium up to whichthe distances are measured in the two projection directions based on thedistances measured in the second projection directions and an angleformed by the two projection directions, and acquire a shortest thirdprojection direction among the third projection directions for each faceof the projection medium as the first projection direction.
 12. Theprojection device according to claim 7, wherein the image processor isconfigured to perform a trapezoidal distortion correction along theprojection direction for the image data and perform the reductionprocess for the image data for which the trapezoidal distortioncorrection is performed.
 13. The projection device according to claim 7,further comprising: a distance value output unit configured to output adistance value that represents the measured distance from the projectionunit to the projection medium; a focus adjusting unit configured toadjust focus of light passing through the projection unit; a focusadjusting/driving unit configured to detect a first deviation from anin-focus state of the light projected onto the projection medium by theprojection unit based on a first distance value by using the distancevalue as the first distance value and drive the focus adjusting unitsuch that a value representing the first deviation becomes zero; adetermination unit configured to detect a second deviation from thein-focus state of the light based on a second distance value by usingthe distance value as the second distance value and determine whether ornot a value representing the second deviation is less than a threshold;and a focus adjusting/controlling unit configured to set the thresholdof the determination unit to a second value larger than a first valueand stop updating the first distance value of the focusadjusting/driving unit in a case where the determination unit determinesthat the threshold is the first value, and a state in which the valuerepresenting the second deviation is less than the first value iscontinued for a time set in advance.
 14. The projection device accordingto claim 13, wherein the focus adjusting/controlling unit is configuredto set the threshold value to the first value and restart updating ofthe first distance value in a case where the determination unitdetermines that the threshold is the second value, the projectiondirection of the projection unit is in the middle of being changed, andthe value representing the second deviation is the threshold or more.15. A projection device comprising: a projection direction changing unitconfigured to change a projection direction of a projection unit thatconverts image data into light and projects the light; a distancemeasurement unit configured to measure a distance up to a projectionmedium onto which the projection unit projects light; a directionacquiring unit configured to acquire a third direction perpendicular tothe projection medium based on distances measured in at least two ormore projection directions of the projection unit by the distancemeasurement unit; and an image processor configured to perform imageprocessing according to a fourth direction acquired by correcting theprojection direction of the projection unit using the third directionfor the image data projected by the projection unit.
 16. The projectiondevice according to claim 15, wherein the direction acquiring unit isconfigured to detect a first inflection point of a downward projectionin a change in the distance measured by the distance measurement unitwhile changing the projection direction of the projection unit by usingthe projection direction changing unit and acquire a projectiondirection corresponding to the first inflection point as a thirddirection.
 17. The projection device according to claim 16, wherein thedirection acquiring unit is configured to further detect a secondinflection point of an upward projection in the change in the distancefor every predetermined interval of the projection direction that ismeasured by the distance measurement unit, and wherein the imageprocessor performs a distortion correcting process according to acorrection coefficient set in advance for the image data and performsswitching the correction coefficient between a third correctioncoefficient and a fourth correction coefficient between before and afterthe projection direction corresponding to the first inflection point andbetween before and after the projection direction corresponding to thesecond inflection point.
 18. The projection device according to claim15, wherein the distance measurement unit measures a first distance anda second distance in a fourth projection direction and a fifthprojection direction for projection for a first face of the projectionmedium, and wherein the direction acquiring unit acquires a thirddirection by using the first distance, the second distance, and an angleformed by the fourth projection direction and the fifth projectiondirection.
 19. The projection device according to claim 18, wherein thedistance measurement unit is configured to further measure a thirddistance and a fourth distance in a sixth projection direction and aseventh projection direction for projection for a second faceintersecting with the first face, wherein the direction acquiring unitis configured to acquire another third direction by using the thirddistance, the fourth distance, and an angle formed by the sixthprojection direction and the seventh projection direction and acquire anintersection between the first face and the second face based on a firstpoint and a second point on the first face at which the first distanceand the second distance are measured and a third point and a fourthpoint on the second face at which the third distance and the fourthdistance are measured, and wherein the image processor is configured toperform a distortion correcting process according to a correctioncoefficient set in advance for the image data and perform switching thecorrection coefficient between a third correction coefficient and afourth correction coefficient between before and after the thirddirection, between before and after a direction corresponding to theintersection, and between before and after the another third direction.20. The projection device according to claim 15, further comprising: adistance value output unit configured to output a distance valuerepresenting a measured distance from the projection unit to theprojection medium; a focus adjusting unit configured to adjust focus oflight passing through the projection unit; a focus adjusting/drivingunit configured to detect a first deviation from an in-focus state ofthe light projected onto the projection medium by the projection unitbased on a first distance value by using the distance value as the firstdistance value and drive the focus adjusting unit such that a valuerepresenting the first deviation becomes zero; a determination unitconfigured to detect a second deviation from the in-focus state of thelight based on a second distance value by using the distance value asthe second distance value and determine whether or not a valuerepresenting the second deviation is less than a threshold; and a focusadjusting/controlling unit configured to set the threshold of thedetermination unit to a second value larger than a first value and stopupdating the first distance value of the focus adjusting/driving unit ina case where the determination unit determines that the threshold is thefirst value, and a state in which the value representing the seconddeviation is less than the first value is continued for a time set inadvance.
 21. The projection device according to claim 20, wherein thefocus adjusting/controlling unit is configured to set the thresholdvalue to the first value and restart updating of the first distancevalue in a case where the determination unit determines that thethreshold is the second value, the projection direction of theprojection unit is in the middle of being changed, and the valuerepresenting the second deviation is the threshold or more.